[Jack of Arcades]

Conduct detrimental to the game.

As to the original question... here's the rule on free throw interference.

b. A player shall not touch the ball or basket while the ball is on or within the basket.
(2) In (b) above, a violation by the defense shall be disregarded if the free throw attempt is successful. If the free throw attempt is unsuccessful, one point shall be awarded.

e. No player shall deflect or catch the ball before it reaches the basket or backboard on a free throw attempt.
(5) In (e), if the violation is by the defensive team, the point is scored and the same player receives another free throw attempt. The additional free throw attempt is considered a new play. This can only occur when the ball will remain in play after the free throw attempt. If it occurs on a free throw attempt which is to be followed by another free throw attempt, only the single point is awarded, and the remaining free throw(s) shall be attempted.

So in order for it to work you'd have to hit it on the brief second it's on the rim, which you might as well just rebound it. If you swat it before it hits the rim, they get another free throw.