Cities can't prosecute people for sleeping on the streets if they have nowhere else to go because it amounts to cruel and unusual punishment, which is unconstitutional, a federal appeals court said Tuesday.

The 9th U.S. Circuit Court of Appeals sided with six homeless people from Boise, Idaho, who sued the city in 2009 over a local ordinance that banned sleeping in public spaces. The ruling could affect several other cities across the U.S. West that have similar laws.

It comes as many places across the West Coast are struggling with homelessness brought on by rising housing costs and income inequality.

When the Boise lawsuit was filed, attorneys for the homeless residents said as many as 4,500 people didn't have a place to sleep in Idaho's capital city and homeless shelters only had about 700 available beds or mats. The case bounced back and forth in the courts for years, and Boise modified its rules in 2014 to say homeless people couldn't be prosecuted for sleeping outside when shelters were full.

But that didn't solve the problem, the attorneys said, because Boise's shelters limit the number of days that homeless residents can stay. Two of the city's three shelters also require some form of religious participation for some programs, making those shelters unsuitable for people with different beliefs, the homeless residents said.

The three-judge panel for the 9th Circuit found that the shelter rules meant homeless people would still be at risk of prosecution even on days when beds were open. The judges also said the religious programming woven into some shelter programs was a problem.