I am not positive.....but I believe it is not allowed. Not sure though. As far as I am concernered......they can do it against me, because the advantages of what they will leave me is good I think. Say they miss hit their jump shot.....might knock a ball off the table, or at best sell out a ball or 2. A log time ago I saw 2 older guys playing for maybe 40 a game or so, and the foul rule came up about touching a ball fouls. One thought if you touched any ball other than the cue ball it was foul, and the other said no it has to be 2 or more balls in order to be a foul. After argueing about it.......one of the guys raked his cue down the table and raked every ball towards his hole...........and said " I guess I owe one! "