Originally posted by batdude123Ring protects against being removed when it has its intelligence. See: Jack T Chance vs Lobo.
They only have automated defense shielding against fatal attacks that they themselves can't track. If Superman decides to steal Hal's ring before he can react, then the ring isn't going to go into automated defense mode. However, Hal still probably wins this 6-7/10.
It can also heal a lantern from completely dismemberment and pretty much anything short of an instant death move, like a rookie falling into a black hole.