NATIONAL BRIEFING / NATIONWIDE

Rules requiring passports or new high-tech documents to cross the United States’ northern and southern borders are taking effect Monday, nearly eight years after the Sept. 11 attacks and long after the 9/11 Commission recommended the changes. They were delayed by complaints from state officials who worried that the restrictions would hinder the flow of people and commerce and affect border towns dependent on international crossings.

In 2001, a drivers license and an oral declaration of citizenship were enough to cross the borders with Canada and Mexico; Monday’s changes are the last step in a gradual ratcheting up of the requirements.