In the past, U.S. citizens only needed to show a valid driver’s license or birth certificate to cross the border. However, there is a new policy, recently enacted, stating that they now much present a passport or specially issued identification card to get back into the U.S.
The law pertains to anyone traveling by car, foot or by sea. Air travelers have had to show passports when returning from bordering nations since 2006.
If you do happen to forget the new law, you will probably not be detained for a month. Although be prepared for a few hours of background checks to prove your U.S citizenship.