For what it's worth here's the rule.
ARTICLE 3. A live ball becomes dead and an official shall sound his whistle or declare it dead:
g. When a scrimmage kick beyond the neutral zone or a free kick is caught or recovered by any player after a valid or invalid fair-catch signal; or when an invalid fair-catch signal is made after a catch or recovery by Team B
The next explains normal rules for a fair catch.
SECTION 5. Fair Catch
Dead Where Caught
ARTICLE 1. a. When a Team B player makes a fair catch, the ball becomes
dead where caught and belongs to Team B at that spot.
b. When a Team B player makes a valid fair catch signal, the unimpeded
opportunity to catch a free or scrimmage kick continues if this player muffs
the kick and still has an opportunity to complete the catch. This protection
terminates when the kick touches the ground. If the player subsequently
catches the kick, the ball is placed where he first touched it (A.R. 6-5-1-I-II).
c. Rules pertaining to a fair catch apply only when a scrimmage kick crosses
the neutral zone or during free kicks.RULE 6 / KICKS FR-67
d. The purpose of the fair catch provision is to protect the receiver who, by his
fair catch signal, agrees he or a teammate will not advance after the catch
(A.R. 6-5-5-III).
e. The ball shall be put in play by a snap by the receiving team at the spot of
the catch if the ball is caught (Exceptions: Rules 6-5-1-b, 7-1-3 and 8-6-1-
b).
No Advance
ARTICLE 2. No Team B player shall carry a caught or recovered ball more than
two steps in any direction after any Team B player gives a valid or invalid fair
catch signal (A.R. 6-5-2-I-II).
No Tackling
ARTICLE 5. No player of the kicking team shall tackle or block an opponent
who has completed a fair catch. Only the player making a fair catch signal has
this protection (A.R. 6-5-5-I and III).
Approved Ruling 6-5-2
I. B1 gives a fair catch signal before a muff by B2, and then B1 catches
or recovers the kick and advances. RULING: Because of B1’s signal
the ball is dead where caught or recovered. Two steps are permitted to
enable B1 to come to a stop or to regain balance. A third or subsequent
step inbounds is subject to penalty from where the ball is caught or
recovered. If B1 is tackled, the tackle is disregarded unless deemed
unnecessarily rough or is so late that the tackler should know that there
was no intention to advance. If the kick is caught or recovered by Team
B in the end zone, it is a touchback. If B1 is tackled before completion
of a third step, only the tackler has fouled.
II. Team A punts. After signaling for a fair catch on his 20-yard line,
B1 deliberately lets the ball strike the ground, where B2 recovers the RULE 6 / KICKS 27
bouncing ball and advances to Team B’s 35-yard line. RULING: The
ball is dead at the spot of recovery. Advance is illegal. Penalty—Five
yards from the succeeding spot, the spot of recovery. Team B’s ball, first
and 10 (Rule 5-2-7).
