From CTV News:
Children under 15 will not have to comply with new laws forcing visitors to show a passport at U.S. land or sea borders, American officials will announce Thursday.
The announcement will be made by U.S. Secretary of Homeland Security Michael Chertoff in Detroit, U.S. State Department sources told The Canadian Press.
The new passport requirements are expected to take effect as soon as January 2008.
I’ve read elsewhere that it is under 17. I’m not sure which it is…