It is up to the rider making a pass to do so cleanly and as safely as possible. This is where holding your line comes into play. Holding your line means I know where you are going and where you are going to be on the track when I get to you, and lets me plan my pass.
Here is a clip where a slower rider enters the turn before me and swings out unnecessarily wide for his speed. It's not an ideal line, but it's his line and that's ok. As I approach, I don't know for sure if he will continue to hold a wide line around the next turn or cut all the way across to the apex. I slow up a bit to let him commit one way or the other. He commits toward the inside and I proceed to go around the outside, but just as I'm pulling along side, he decides to change his line and move back toward the outside forcing me to stand the bike up a bit to avoid a collision. Had he held his line, the pass would have been clean with 6 feet of cushion between us.
Perhaps I could have maintained my speed from the beginning and zoomed up the inside, but that would have risked a collision, or I could have spooked him forcing him to run off track in a not so friendly run-off area. I chose to go with the more cautious approach for both our sakes. That's it boys and girls. Have fun, hold your line, be predictable and be safe!