California authorities have agreed to sharply limit the number of inmates held in isolation for long periods of time, a major development in the national debate about solitary confinement.

The agreement resolves a class-action lawsuit filed by prisoners who say the practice amounts to cruel and unusual punishment. Advocates say it could change the daily lives of as many as 2,000 inmates stuck in isolation because authorities determined they had some ties to a gang.

The inmates live in tiny windowless, sound-proofed cells for nearly 23 hours each day — some have remained there for decades.

Originally published here on npr.org.