system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Wars][Old Republic] What does the Jedi Order do when one of its members is discovered to be using the Dark Side?
gpt
Assuming "using the dark side" isn't "murdering everyone in sight," the first thing to do is try to talk to them about it. Point out that their behavior leads down an all-too-familiar path, and council them on how to do better. We see Yoda try this (unsuccessfully) on Anakin in Episode II.

If the force user is at the murdering stage, then there's nothing to do but put them down.

Some dark side users will at least have enough self-preservation to realize that what they're doing is not accepted by the Jedi Order, and simply go into self-exile. It's a big galaxy, and the Jedi don't try to enforce membership in their order, so it's easy enough to slip away. It's up to the former Jedi whether or not they'll lash out at any Jedi they see, at which case a follow-up session may be scheduled, preferably with a Jedi master who can engage in the appropriate negotiations.