Chris Landry, 46, was stopped Sunday at the border in Houlton, Maine, on his way back to Peterborough, New Hampshire.

The 46-year-old moved to America as a toddler, and now has a wife, five children, a job, and a home. But when he tried to re-enter the U.S., he was stopped by border agents.

Eight-year-old girls at sleep-away camp, families crammed into recreational vehicles, local residents traveling to or from ...