[The Roamin' Umpire]

2-9-3: A valid fair-catch signal is the extending and lateral waving of one arm, at full arm's length above the head, by any member of the receiving team. (Note: No reference to the field position of the receiver.)

4-2-2g: Following a valid or invalid fair-catch signal given by any member of the receiving team when a scrimmage kick or free kick is caught or recovered by any member of the receiving team beyond, in, or behind the neutral zone.

6-5-5: No receiver may advance the ball after a valid or invalid fair-catch signal has been given by any member of the receiving team.

In short, if R signals and they possess the kick, kill it.