it is defensive intentional grounding and there has to be a penalty for the foul!

9-9-1 gives you the latitude to do so.

I don't even need to go there. There's a rule that covers this.

3-6-2 Action or inaction which prevents promptness in putting the ball in
play is delay of game. This includes:

d. Failure to properly wear legal or required player equipment when the ball is
about to become live.

PENALTY: Delay of game – (Art. 2d) – (S7-21-23) – 5 yards;