The rules for one pocket say explicitly that the only foul for which the pocketed opponent's ball comes back onto the table is pocketing the cue ball. If some other foul is committed, you keep the ball.
Also.... In a lot of modern tournaments, you are not allowed to drive the cue ball off the table for the foul. It's too dangerous and/or unseemly.
Here is the pertinent wording from the WPA version of the rules of one pocket:
Each ball legally pocketed in one of the foot pockets counts one point for the corresponding player. In addition, balls pocketed in the opponent’s pocket on a foul shot count for the opponent and are not spotted under 10.6 below unless the only foul committed is that the cue-ball is also pocketed.
). For me, that's really good and no doubt I'm biased by using it a lot, and getting used to it, but it's a darn good cue. I got the weight kit and what the heck, I'm going to do a little experimenting with it here in a little bit - might as well understand how it works and whether I like a different feel.
