I've never seen it happen, but theoretically, it is possible. What has happened so far is that after their Desires were stolen in the Metaverse, a change of heart occurred. They confessed their wrongdoings and vowed to change their behaviour. The risk of doing it again is there, since the Jail and the EMMA app haven't vanished.

[She hesitates briefly, then admits,]

Eliminating them would be more efficient. But the Phantom Thieves don't kill. And saving all the victims, even the Monarch Shadow, makes everyone... happier.