In a 407-19 vote on December 8th, the House tightened controls on travel to the United States and will require visas for anyone who has been in Iraq, Iran, Sudan or Syria in the last five years. Exceptions are made for official government visits and military service. The legislation was driven by the recent attacks in Paris, and was signed into law by the president on Friday.

This is a change to the ESTA visa waiver program which allows citizens from 38 countries to travel to the US for stays of up to 90 days without first obtaining a visa. Countries in the program would also be required to share counterterrorism information with the US or face expulsion from the program.

Currently some 20 million visitors come to the US annually under the visa waiver program. It is unclear how the changes will be implemented, a process which is led by the US Department of Homeland Security.