In a youth game with bases loaded and two outs a ground ball was hit to the pitcher, who made a throw to third base. The throw was low and the third baseman did not field the ball cleanly, so the runner was initially called safe. On appeal he was called out by league rule forbidding head first slides into bases (which he had violated). However, the run remained on the board. Should this have been a force out and the run removed?
I'd say yes. If the illegal slide had been made before the run was scored, then the third out was made at that point and the half-inning was retired, without the run scoring.
The only way it would count is if both the run scored and the hitter had safely reached first base, before the out at third was made, but that sounds rather unlikely. For more on this see this question.
I will say no, this would not count as a force out.
There are 2 typical courses of action when a baserunner is called out due to a violation of the rules:
For cases of interference, whether with a batted ball, a throw from a fielder, or a shortstop attempting a double play, the runner is out and the ball is dead. If this were the ruling of the headfirst slide rule, the runners would have to return to their previously touched base before the interference, and the run would not have scored unless that runner had already touched home, regardless of number of outs. It would not be a force out.
For cases of runners passing each other on the basepath, or a runner running out of the basepath, there is not a dead ball and play continues. In this case again, the run would score if there were less than 2 outs or the runner touched home plate before the incident occurred.
In either case, the out would not be treated as a force out and the run would score, as long as the runner had touched home plate before the incident occurred.