Federal agents set up shop in New Hampshire last week. They ran a Constitutionally-illegal checkpoint, violating the Fourth Amendment rights of countless Americans. The big reward? They arrested 25 illegal immigrants, seven of them children. More than half of those detained had overstayed visas. That means they came to the U.S. legally in the first place and did not leave when their visa expired. What could have spurred this callous disregard for the law? Well, a personal anecdote could shed some light on the situation. A friend of mine from Brazil had a six-month visiting visa to the United...