Most people understand golf as a game where golfers hit a stationary ball. The ball doesn’t move when a golfer makes a stroke, and that’s one of the most taunting parts of the sport. It’s there staring at the golfer the whole time.
So, under the Rules of Golf, it’s expressly illegal for a golfer to hit a ball or putt a ball while it’s still moving — be it bouncing, rolling on the putting surface or even in the air. The ball has to be at a complete stop when a player hits it, or otherwise the golfer is breaking Rule 14-5.
From the Rules of Golf, here’s Rule 14-5:
A player must not make a stroke at his ball while it is moving.
When the ball begins to move only after the player has begun the stroke or the backward movement of his club for the stroke, he incurs no penalty under this Rule for playing a moving ball, but he is not exempt from any penalty under Rule 18-2.
A player is excepted from the rule when the ball is on the tee, is moving in a water hazard or is struck more than once.
Now, there’s also the consideration for a “serious breach” of the Rules of Golf, which would cover when a golfer hits a ball while it’s still moving knowing that it would help them save strokes or was a violation so blatant it was unbecoming of a golfer. In that case, the player would then be disqualified.
There’s also consideration under Rule 1-2, which would constitute when a player is “taking action with the intent to influence the movement of a ball in play.” That would mean stopping or deflecting the ball so as to gain an advantage. The penalty for that is disqualification.