U.S. Border Entry Laws and Regulations

In the wake of the terrorist attacks on September 11, 2001, the United States border entry rules became stricter. Immigration policies did the same.

As a consequence of anxieties about terrorism, illegal immigration became a much bigger concern in the United States. Even legal immigration became harder. New policies concerning visa applications, naturalization, and asylum seekers went into effect.

This article highlights basic border entry rules. It addresses:

• How 9/11 impacted border crossing laws today
• Border crossings by U.S. citizens and legal permanent residents
• Border crossing rules that affect green card holders
• Policies that affect citizens of Canada, Mexico, Bermuda, and visitors from other countries.
• U.S. Customs and Border Protection’s (CBP) Trusted Traveler Programs for low-risk visitors

Border security policies shift and enforcement varies. Understanding the current border regulations can help prevent delays or complications at ports of entry. Talk to an immigration attorney near you for targeted, up-to-date legal information.

Crossing the Border Post 9/11

Federal agencies, most notably the Department of Homeland Security (DHS) and its U.S. Customs and Border Protection (CBP) division, are tasked with balancing the need for border security with the desire for an efficient and welcoming border entry system.

Under the Immigration and Nationality Act (INA), the U.S. immigration system had once been easier to navigate. But in the post-9/11 world, the U.S. was no longer as accommodating for those crossing the border as it once was. Wait times for visa issuances grew longer. Even foreign students experienced delays in obtaining student visas. In general, migrants and noncitizens faced far more obstacles in determining eligibility for visas and entering the United States.

U.S. Citizenship and Immigration Services (USCIS) experienced greater backlogs of visa applications. The same was and remains true for citizenship applications. It was no longer as easy to obtain citizenship for employment-based reasons. It was even harder to obtain a green card. Even temporary workers struggled to enter the U.S.

Those who already had a U.S. citizen family member had once received priority in the citizenship application process. This once meant shorter wait times for citizenship for people who met this criterion. However, in the post-9/11 world, this was no longer the case. Across the board, the naturalization process became more difficult. Along with many other government departments, the U.S. Department of State instituted far stricter policies at the consular and USCIS levels.

The new policies were expansive. U.S. citizens have always needed to present a valid passport when crossing the U.S. border by air or land. This did not change after 9/11. But those with U.S. residency and legal permanent residents often faced greater suspicion when attempting to move through U.S. ports of entry.

However, they also needed to provide appropriate travel documentation. This has always been true. Visitors from other countries found it harder to travel to the United States. It is also true that those crossing the U.S. border by land or sea have not always been required to present a passport or other documentation.

But in the wake of 9/11, policies were stricter. More and different documentation became required. This depended on factors like country of origin and immigration status.

U.S. Citizens

All U.S. citizens traveling by air for international travel must present a passport or other approved travel document. Some qualifying documents include the following:

• U.S. military ID with travel orders
• U.S. Merchant Mariner document when travel is on official business
• NEXUS card under the trusted traveler program where the port-of-entry permits

U.S. citizens returning by land or sea must present a passport or document that complies with the Western Hemisphere Travel Initiative (WHTI) restrictions, such as a NEXUS card. A NEXUS Card is a preapproved card for low-risk travelers. It helps speed up the border entry between the United States and Canada.

Also, Congress passed the REAL ID Act, which took effect on May 7, 2025. This law requires every traveler 18 and older to present an acceptable form of ID when flying domestically within the United States. Because of changing rules, it is crucial to stay up to date on travel advisories and changes in immigration law.

Lawful Permanent Residents (Green Card Holders)

As with U.S. citizens, lawful permanent residents (LPRs) must also present a passport or secure travel document when entering the U.S. by air. When crossing the border by land or sea, LPRs may present their Permanent Resident Card (Form I-551).

Different rules may apply for LPRs waiting for their green card. For instance, green card applicants planning to stay outside the United States or travel to their home country should also get an Advance Parole Document. This document should be secured to avoid issues with abandonment of residency.

Citizens of Canada, Mexico, and Bermuda

Special rules apply to Canadian, Mexican, and Bermudian citizens crossing the U.S. border as part of the WHTI. All international visitors must present a passport or secure travel document when entering the country by air. They must do so regardless of their country of origin.

Some acceptable documents include SENTRI, FAST, NEXUS, Enhanced Driver’s License, and Global Entry Cards. Most of the documents are part of the Trusted Traveler Programs. These are designed to speed border crossing, reducing wait times.

See CPB’s interactive WHTI map for more detailed information.

• Canadian Citizens: Must present a single WHTI-compliant document when visiting by land or sea. Some Canadian citizens are subject to US-VISIT biometric procedures.
• Bermudian Citizens: Must present a single WHTI-compliant document when visiting by land or sea. All Bermudian citizens are subject to US-VISIT biometric procedures.
• Mexican Citizens: Must present a passport with a nonimmigrant visa or laser visa border crossing card when visiting by land or sea. Some Mexican citizens are subject to US-VISIT biometric procedures.

All Other International Visitors

International visitors to the U.S. typically must show a U.S. passport or e-Passport when going through customs. Visitors from certain countries may enter the U.S. without a visa. They may do so under the Visa Waiver Program. 

They are subject to the internet-based Electronic System for Travel Authorization (ESTA). This applies before traveling to the U.S. Those entering the U.S. on a visa are subject to US-VISIT biometric screening procedures.

Trusted Traveler Programs

CBP’s Trusted Traveler Programs encompass various types of pre-screenings. These expedite travel through dedicated lanes for travelers deemed low-risk.

• NEXUS: For approved members between the Canada and U.S. border for land, sea, and air entry
• SENTRI: For approved members between the Mexico and U.S. border for land, sea, and air entry
• FAST: For approved commercial truck drivers between Canada and the U.S. and Mexico and U.S. borders
• Global Entry: For pre-screened international travelers to the U.S

Questions About Crossing the Border? Get Legal Answers

Immigration laws are constantly changing. Several factors can cause confusion for those entering the United States. Among those are executive orders and changes to laws related to border crossings. What was true yesterday under one president may not be true under another. An immigration lawyer can provide the latest legal guidance and address any issues, concerns, or questions you may have about crossing the U.S. border.

FindLaw’s directory of immigration attorneys can get you started. Enter your city or ZIP code for a list of qualified legal professionals in your area. Your search results will also show important details about prospective lawyers, including ratings, languages spoken, and whether they offer free consultations.