A Sith Lord might be able to force choke a Green Lantern if he did it quickly and that would be a force users only chance. A Green Lantern would crush whole groups of Jedi with ease. Not even Yoda or Darth Sidious would have much of a chance. A Lantern Corps member can create an energy shield around their body, rendering the lighsaber ineffective. The ring doesn't have any moveable parts that can be telekinetically manipulated and even if they pull the ring from ring users body, they can still mentally activate the ring.