For years, San Francisco has struggled to deal with encampments crowding sidewalks, and the authorities have said that some tents have been used as cover to sell and consume drugs — particularly fentanyl, which has contributed to a spike in deadly overdoses. The city lacks enough affordable housing, drug treatment programs and hospital beds to address the misery, and voters are steamed.

The mayor told reporters last week that she was “excited” about the Supreme Court, dominated by Republican appointees, upholding the ban in Grants Pass, Ore., on homeless people sleeping outside. For several years, the U.S. Court of Appeals for the Ninth Circuit, which oversees nine Western states including California, had blocked laws that made it illegal to camp when no shelter was available.

Governor Newsom’s recent order directed state officials to begin dismantling thousands of homeless encampments and urged local leaders to follow suit. Ms. Breed praised the enforcement approach, noting that her teams repeatedly offer shelter beds, but are turned down two-thirds of the time.

But advocates for homeless people called it cruel, saying it would do little to solve the underlying factors that lead to homelessness. City and county leaders in Los Angeles have criticized both the Supreme Court and Governor Newsom and vowed to solve homelessness in their own way, primarily by finding motel space and services for people before clearing them from the streets.

In San Francisco, however, a police officer this week told one homeless person that tents were being swept in the city because Ms. Breed and Mr. Newsom had declared “no more on the streets, no more encampments,” The San Francisco Standard reported.