The U.S. Supreme Court heard oral arguments Monday on whether it's constitutional for cities to ban homeless residents from sleeping outside when shelter space isn't available. Why it matters: District Attorney Summer Stephan argued in a brief that the lower court's opinion creates "uncertainty about the validity" of the unsafe camping ordinance San Diego adopted last year.

Hundreds of protestors gathered outside the Supreme Court, lying down under blankets to show their solidarity with the people at the center of the case.

Demonstrators — some of whom had been homeless themselves — came from New York City, Philadelphia and other cities to protest outside the Supreme Court.