One evening in August 2011 when Jaenean Ligon was making chicken and French fries for dinner, she sent her 17-year-old son out to buy ketchup. On his way back to their apartment building in the Bronx, he was intercepted by several police officers, who questioned him, frisked him, and would not let him go until his mother came down to confirm that he lived there.

In January, a federal judge concluded that such demeaning encounters seem to be part of a pattern. U.S. District Judge Shira Scheindlin ordered the New York Police Department to stop routinely detaining and frisking people outside buildings in the Bronx under the so-called Trespass Affidavit Program (TAP). The program, conducted in cooperation with landlords, is supposedly aimed at trespassers, but Scheindlin found that police frequently harass tenants and visitors who have a right to be where they are.

“While it may be difficult to say where, precisely, to draw the line between constitutional and unconstitutional police encounters, such a line exists, and the NYPD has systematically crossed it when making trespass stops outside TAP buildings in the Bronx,” Scheindlin wrote. “For those of us who do not fear being stopped as we approach or leave our own homes or those of our friends and families, it is difficult to believe that residents of one of our boroughs live under such a threat. In light of the evidence presented at the hearing, however, I am compelled to conclude that this is the case.”

Scheindlin emphasized that the Fourth Amendment requires “reasonable suspicion” that someone is trespassing before he can be stopped by police as an allegedly unauthorized intruder. The fact that someone has entered or exited a building is not enough, she said, and neither are “furtive movements” or the target’s presence in a high-crime area, rationales frequently offered by police on forms documenting their stops.