Forget your underwear, socks and toothbrush - leaving the U.S. requires packing more important things.
The U.S. Border Patrol changed the travel-document requirements for U.S. citizens in January after Congress passed the Intelligence Reform and Terrorism Prevention Act of 2004.
In order to re-enter the U.S., people must show their passport or a driver's license and birth certificate.
Previously, people could declare American citizenship to be allowed into the U.S.
Brian Levin, public affairs officer for U.S. Customs and Border Patrol, said people can still re-enter the country if they forget their documents - but not without a lecture.
They will also be given information about the documents that are needed, he said.
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"We're in a public education phase," he said. "In June of 2009, a requirement is going to go into effect that all U.S. citizens coming in by land or by sea is going to have to have a passport."
Student Mike Coffey said he and eight friends will to Mexico over break.
Coffey said he has known about the new requirements for a while and will take his driver's license and passport.
Joan Cok, program supervisor for UNM Community Education programs, said she took a group of students to Cuernavaca, Mexico, right after the requirements changed.
None of her students had a problem re-entering the U.S. because they were prepared, she said.
"They brought a passport, and that was basically all they needed," she said.
Levin said Border Patrol can look up the names of U.S. citizens if they forget their documents.
"U.S. citizens are not going to be denied entry if they don't have their documents on them," he said. "They're not going to be stranded in Mexico, no matter what."
