The Past and Future of Borders

By Alan Bersin
18m read

Borders as Lines

The purpose and function of borders in world history has been and remains to delineate and demarcate - that is, to differentiate one sovereignty from another. They are the juridical lines on a map, indicating the geographical place where imperial and/or national dominion begins and ends. These shift over time as a result of political and military developments, usually followed by legal recognition or acknowledgment expressed in one form or another. History tells the tale of these developments and shifts. Like laws, borders embody and reflect history's results with the narrative left out. 

The importance of borders has been highlighted since the Peace of Westphalia in 1648, which is commonly considered the origin of the modern international system of nation states. The Treaty of Westphalia ended the Thirty Years War and gave rise to a new approach to sovereignty. The revised concept of national authority linked respect for the nation state and the scope of government dominion and control over a subject population to a specific territory defined by formal boundaries. Principles of mutual recognition, jurisdiction, equality, and noninterference became established tenets of the international system. From the 17th century onward, nationalism became a central driving force of political history, in each case tied to very specific notions of border boundaries and place demarcating the edges of sovereign states according to the Westphalian system. 

Borders define a homeland. They are the primary reference points for national defense strategy and homeland security policy. Throughout history, borders have been the site of fortification, intended variously to shut in or keep out people or things. China's Great Wall in the second century BCE, France's Maginot Line pre-World War II, the Soviets' Berlin Wall in the twentieth century, and America's Southwest border fence in the twenty-first century all serve to illustrate the point. It was made more poetic and timeless by Robert Frost in "Mending Wall” where he wrote: "Good fences make good neighbors." So, we see, borders are lines with real result and consequence. When we walk to the riverfront in El Paso and wade into the Rio Grande, at midstream it becomes the Rio Bravo and Juarez, Mexico begins. Without more, one crosses the line (la línea) from one of the safest cities in the Western Hemisphere (five homicides in 2010) to its most dangerous (3,400 homicides in 2010). Border lines matter but rarely account by themselves for the changes they embody.

The spaces of borders, corresponding to their map lines, are marked by ports of entry and exit. It is here where cross-border transactions of people and goods are processed through the exercise of immigration and customs authorities. Typically, the scope of these border inspection authorities is most broad regardless of the legal system under which they operate. Sovereignty asserts itself aggressively at the border threshold to determine who and what has the right or privilege of entrance and exit. The levying of customs fees and duties has generated critical revenue streams for governments since biblical times. It was no accident that one of the earliest acts of the First Congress during the Washington Administration was to establish the U.S. Customs Service in 1789. 

Borders as Flows 

This essay addresses the massive paradigm change that has taken place since 9/11 in our perception of borders not only as lines, but also as movements: flows of people and goods on a global scale both legally and illegally. 

Global flows are not new. These have occurred since ancient times and are chronicled in the ages of discovery and exploration as seafaring matters, and much earlier in the movement of goods and people along the Silk and Tea Horse Roads into China and the caravan paths across Arabia. Nor is the contemporary scale of the flows itself a distinguishing factor. These have increased exponentially century after century, spurred by colonial empires and trading companies, activities multiplied throughout by the growing logic of comparative advantage. The intensity, volume and speed of commercial and migratory flows accelerated mightily with the Industrial Revolution, and then massively again more recently by the invention of the jet engine and the Internet. 

The cumulative effect of these trends is what we refer to as globalization: extraordinary cross-border flows of capital, goods, people, ideas, and images occurring routinely on a daily basis, facilitated by the digitalization of information that has created the reality of instantaneous communication and transaction. As the process of globalization expands, the concept of "borders" is enlarged to encompass the unprecedented flows that cross border lines continuously on a 24/7/365 basis. Borders then are channels and points of flow as much as lines marking national sovereignty. 

Security as the Organizing Principle: The Searing Impact of 9/11 

The trauma of 9/11 inflicted by al Qaida on the world through the United States assured that we would never view cross-border movements in quite the same way. Transnational terrorism exploited the relative openness of borders and laxness of border regulatory regimes to invade the continental United States for the first time since the British burned government buildings in Washington during the War of 1812. 

In one fell vicious swoop that was actual and deadly, and unlike the potential threat we had grown accustomed to during the Cold War, the events of 9/11 altered America's view of security forever. The resulting sense of insecurity stemmed from the fact that its borders had been violated. The reflexive response was to hunker down behind traditional concepts of borders as lines of defense. All planes were grounded and maritime and aviation borders were closed in the immediate aftermath of 9/11. Similarly, land borders virtually shut down as each entering vehicle from Mexico and Canada was inspected thoroughly. In other less visible ways, America closed its borders through restrictions on the issuance of visas and other immigration benefits. As Edward Alden has documented, many of these restrictions pertaining particularly to the grant of visas persist today.

But all the emergency measures taken immediately after 9/11 collided head-on with the realities of global travel and commerce through transit zones and supply chains. They also directly challenged America’s self image as an open, free, and welcoming society. The unacceptable economic and political consequences of shutting down the border, coupled with the new security imperative, forced a fundamental shift in perspective. Americans began to understand that their borders begin not where their ports of entry are located, but rather, where passengers board air carriers and freight is loaded on maritime vessels bound for those ports of entry. In order to forge practical arrangements to take both travel and trade security into account, borders needed to be viewed and managed as flows of people and goods as much as lines in the sand, on the water, or through the air. 

In the ten years since 9/11, three terrorist plots targeting the United States involved cross border movements of people or goods. Each event makes the case powerfully for the new border paradigm that links jurisdictional lines to flows toward them. 

The first involved the so-called underwear bomber, Nigerian citizen Umar Farouk Abdulmutallab, who boarded a plane in the Netherlands intending to ignite PETN explosive material and blow up a Northwest Airlines flight over Detroit. Based on its targeting capabilities, the US Customs and Border Protection Agency ("CBP') identified Abdulmutallab as a person of interest after the flight departed. When the plane arrived in the United States and he presented himself for admission, officers would have referred him to secondary inspection for significant interrogation. This obviously would have been too late, because had he succeeded, he would have blown up the plane before it landed. Border security in this context requires that Abdulmutallab be prevented from boarding the plane in the first place. For these purposes, the border became Schipol Airport in Amsterdam, and the goal changed to the identification and preemption of high risk individuals in the flow of passengers at their last point of departure toward the United States. 

The second case was Faisal Shahzad, the Times Square Bomber, a naturalized U.S. citizen born in Pakistan, who went abroad to receive training from the Taliban in the tribal borderlands between Afghanistan and Pakistan. Shahzad received support and resources in the New York metropolitan area from abroad to construct an explosive device he intended to detonate in Times Square. Foiled by an alert guard, Shahzad attempted to flee the country on board an Emirates Airlines plane. Advance passenger manifest information received by CBP regarding the outbound flight, coupled with significant travel history data available concerning Shahzad, facilitated his identification and apprehension on the tarmac at JFK seconds before takeoff. 

The third terrorist plot was the shipment of parcel bombs by al Qaida operatives in the Arabian Peninsula via UPS and Federal Express. Sent from Yemen, addressed to locations in Chicago, the improvised explosive devices passed through airports in London and Dubai, after having been concealed in printer cartridges and timed to detonate over the United States. As a result of intelligence-sharing by Saudi authorities, we were able to deploy public- and private-sector resources to locate the packages before they reached their intended destinations. As in the other cases, the key lay in the collection, analysis, and sharing of data regarding the transnational origin, route, and flow, in this instance, of express carrier packages. 

Since 9/11, we have learned that the border begins where airplanes take off and where cargo is loaded into the hold, not at the destination boundaries themselves. Homeland Security from this point of view is inherently transnational: there is virtually no adverse impact on the homeland today that does not have a cause or effect generated abroad. The earlier that we can identify, intercept, and neutralize threats to the homeland, the safer people will be. The further away geographically from the physical line that we can achieve these ends, the safer each country will be. 

Border Lines and Global Flows

In the years since these events, time and time again we have seen the transnational nature of homeland security demonstrated in the context of threats to internal safety entirely apart from terrorism. These can be man-made as in the case of migrant surges into Europe and North America and the cartel-fueled fentanyl scourge in the United States, or entirely natural in origin in the manner of the earthquakes in Haiti or the 2010 floods in Pakistan; or they can be attributed to some combination of the two as in the pandemic challenges posed by Ebola, SARS, H1N1, and COVID-19 diseases. The causes and effects of these harmful events do not respect Westphalian borderlines. Nor are they controlled by nation-states. To the contrary, they increasingly are the product of non-state actors including transnational criminal and terror organizations, multinational corporations, as well as Mother Nature. For this reason, they often are referred to as "borderless" in nature.

The starkest exemplar of a borderless world in the traditional sense is presented by the cyber sphere which also illustrates most extremely this notion of borders as encompassing flows. The domain of cyberspace may dispense altogether with the border as a line except to situate a point of transit and damage, or the arc of a censor's official reach. It seems likely that national borders may become increasingly irrelevant in defining lines in the cyber sphere, while flows prevail as analytical and regulatory concepts.

Homeland Security and Global Flows

The goal of border security is keeping dangerous people and dangerous things away from the homeland. In a transnational setting, homeland security/internal defense requires securing the movement of goods and people, among other flows, heading toward the Border Line. Borders are "pushed out" and "externalized." Time and space are enlisted as allies to enhance security as far away geographically from the border boundary as possible and as early as practicable before arrival at the port of entry. 

Authorities are exercised, and resources utilized to identify, intercept and neutralize threats to the homeland, well before they arrive at a port of entry on the border line. This altered paradigm regarding the border security mission has fundamental implications for a border management agency's strategic and tactical approach to organization and function, as well as to its relationships with other agencies both within and outside the government.

Fragmented border management within and between nations is a "Westphalian" artifact of history that globalization requires revisiting. The focus of the new border management paradigm is to collect and analyze information on the flows that move toward sovereign borders rather than merely interacting with people and goods at the lines which divide nations. The risk management paradigm operating with advance information is much more effective than trying to screen everything and everyone at ports of entry on the border line.

Risk Management as the New Border Security Paradigm

If borders are flows of people and goods, and electrons, then those charged with securing and regulating those flows must confront the reality that an estimated ninety-eight percent of the traffic is composed of lawful and compliant trade and travel. The objective to identify and interdict dangerous passengers and cargo (and cyber attacks) from among an otherwise entirely legitimate mass generates a requirement to surgically distinguish between high-risk and low-risk subjects. 

Short of examining every piece of straw separately, there are only two ways one can find the proverbial needle in a haystack. The first is to have very specific insight about where the needle is so that you can reach into the middle of the haystack and pluck it out. That is what occurred in the case of the UPS and FedEx parcels from Yemen. We received very concrete information and were able to reach into the global flow of millions of packages then in transit and ferret out the precise two packages laden with explosives. Through recent advances in machine learning, we can predict the existence of the same proverbial needles with high confidence. Learning from patterns in data across the global trade network, including the results of inspections and enforcement actions, machine learning models are trained to target specific forms of risk, as well as to uncover anomalous activities that might indicate unknown risks requiring inspection or interdiction. 

The second principle of border risk management is to make the haystack smaller. And the way to make the stack smaller is to differentiate routinely between high- and low-risk subjects, and expedite movement of the latter through the global system. Segmenting traffic flows according to risk is a necessary condition of heightening border security at any level of resource allocation. We expedite lawful trade and travel through border controls so that we may focus our scarce regulatory and inspectional resources on that traffic about which we have derogatory information, or about which we lack sufficient information to make a sound judgment regarding its legitimacy. Moving ordinary travelers and regular cargo quickly through ports of entry, therefore, is not only good for the economy, but given the volumes we confront, it is essential to the security function itself. Expediting trade and heightened security, accordingly, are neither antithetical to one another nor are they mutually exclusive matters requiring balance. To the contrary they are part and parcel of a single process. 

False Dichotomies: Security vs Facilitation and Security vs Privacy

The long-held view posits that security and trade, and security and privacy, are independent variables competing in a zero sum game. According to conventional wisdom, trade facilitation, the expedited movement of commerce, and security, ensuring the safety of that commerce, must be balanced to an optimal equilibrium. The concept of "so much security" in exchange for "so much delay" in the processing of trade has governed port of entry operations for generations. Similarly, the imperative of data sharing in risk assessment and targeting is often met by objections around data privacy and data sovereignty. 

Risk management, however, powered by modern technology advances, leaves these notions not only theoretically false but also practically outdated and self-defeating. 

Modern Technology for Border Risk Management

Advance information on global flows becomes central to the evaluation of risk, while data are the building blocks of timely and actionable information. The exploitation of aggregated and linked transnational data is not just desirable but also absolutely necessary in border management given the other far less attractive options available to secure global flows. 

In order to shrink the “haystack” and target the “needles,” it is first necessary to clean, connect, and harmonize datasets describing global trade and travel networks that are otherwise disorganized, hard to access, and disconnected. Doing so creates visibility and context for risk targeting algorithms. Joining public and commercially-available data can help by creating a reference set on global networks and flows. Joining this reference dataset of public data with non-public data available to border protection and revenue authorities then shows the connections and flows of people, companies, transits, and transactions at and beyond the border. 

Recent technological advances enable the real-time processing and risk analysis of data on border flows. This involves ingesting advance information, such as cargo manifests of ships nearing a port of entry, resolving the data therein to ground-truth data and reference data, and modeling the combined data to determine the risk characteristics (high or low) of every border flow. Performing these data fusion and analytical tasks across disparate datasets - many of which are unstructured or semi-structured - in close to real time and on every border flow, is a massive technical challenge only recently possible owing to advances in cloud computation, natural language processing, and machine learning.

Sophisticated, automated risk targeting entails the combination of watchlists and human-specified rules with modern machine learning, in order to detect from transnational data both known and unknown threats. Similarly, these risk scoring algorithms help to identify low-risk flows and promote them for expedited clearance. Targeting in this fashion increases our capacity to generate signals and discover the dangerous people and dangerous things for which we are on the lookout at the border without slowing down each border-related transaction to inspect it.

Recent advances in data management facilitate access to shared intelligence across sensitive datasets with robust guarantees on data privacy, intellectual property entitlements, and sovereignty of that sensitive data. Federated learning and anonymization avoid direct exchanges of data in favor of carefully tailored techniques of access, with audit trails and data provenancing to ensure compliance with the agreed legal restrictions. Sensitive information such as personally identifiable information in data can be redacted from shared data, while the use of cryptography enables the linking of information that yields risk signals across the redacted datasets. Similarly, federated machine learning enables key insights from data to be gleaned, and even shared, across multiple data owners without any transfers of the underlying data. The only information that is "shared" is learnings across federated datasets. Techniques such as differential privacy ensure that sensitive data cannot be reverse engineered from the signal. Through these and related methods, data sovereignty and privacy are preserved.

Through federated machine learning, these values - data sharing and privacy - turn out not to be necessarily in conflict. Nor are security and trade facilitation mutually exclusive.


Nation-states remain the forum of geopolitical calculation and activity in the contemporary world. However, transnational factors increasingly dominate what matters in the internal as well as external security and economic theatres. Border management has become inherently transnational. There is nothing - human-made or natural - that affects the homeland adversely which does not now have a cause or effect that is generated outside its border lines. This has led to the so-called “pushing out” of borders. The externalization of borders is breaking down old dichotomies and definitions by which policymakers and analysts in the past drew distinctions with a difference, as for example between “foreign” and “domestic” affairs or between “national security” and “homeland security.”  The subject matter and objectives of these missions more frequently overlap. This type of adjustment in nomenclature classically is a leading indicator of a “paradigm shift,” or dramatic transformation in conventional wisdom.

Technology and globalization have brought the world to a turning point. The inadequacies of Westphalian governance, and the limitations of conventional wisdom and traditional process, have become painfully evident in the increasing inability to control transnational illicit flows and the criminal activity generating them. In technology lies a solution. The systematic application of artificial intelligence to data fusion, targeting, screening and traffic segmentation holds out great promise both for securing the global flow of goods and people and expediting lawful trade and travel. Our era is one of dramatic, disruptive transition. It calls for innovative reinvention.


Alan Bersin is the Executive Chairman of Altana AI. He served as Commissioner of U.S. Customs and Border Protection (2010-2012) and as Assistant Secretary of Policy and International Affairs and Chief Diplomatic Officer at the Department of Homeland Security (2012-2017). He served previously as United States Attorney in the Southern District of California and the Attorney General's Southwest Border Representative ("Border Czar") during the Clinton Administration. He serves currently as an inaugural Senior Fellow in the Homeland Security Project at the Belfer Center at the Harvard Kennedy School of Government; as a Global Fellow at the Woodrow Wilson Center for International Scholars in Washington D.C.; and as Inaugural North American Fellow at the Canada Institute and the Mexico Institute (Wilson Center).