what law limits the crossing over into Mexico or vice versa?

The law that limits crossing over into Mexico or vice versa is called immigration law. Immigration laws are in place to regulate the entry, stay, and exit of foreign nationals from a particular country. These laws vary between countries, and in the case of Mexico and the United States, each country has its own set of immigration laws that govern the process of crossing the border.

To understand the specific laws and requirements for crossing the Mexico-United States border, you can refer to the immigration laws of both countries. For instance, in the United States, the primary immigration law is the Immigration and Nationality Act (INA), which defines the legal procedures for entering the country, obtaining visas, and determining eligibility for admission. Additionally, the U.S. Customs and Border Protection (CBP) enforces immigration laws at the Mexican border.

For understanding Mexico's immigration laws, you can refer to the Ley de Migración (Migration Law) introduced in 2011, which outlines the requirements and procedures for entering and staying in Mexico as a foreign national. The National Institute of Migration (INM) is the Mexican governmental agency responsible for enforcement and implementation.

It's important to note that both countries have specific rules and regulations regarding visas, passports, entry points, and the reasons for entering the country. It's advisable to consult the official government sources or immigration authorities of each country for the most accurate and up-to-date information before planning any international travel.