LJDave,
See rule 6-5-3

We need to change you believe as fair catch protection does not applies to a receiver who has made an invalid signal. Sure the play is over when caught, but the receiver might be contacted before the whistle has signaled the end of the play. If this contact is of such intensity, or say by the face mask, you can have a foul on K, but it is not kick catch interference. 6-5-3.

While looking at 6-5-3 you must also review 6-5-6 as while a receiver who gives a fair catch signal is afforded protection a receiver who has not given a fair catch signal must be afforded the opportunity to catch the ball.

The concept of the Fair Catch is simple, R forfeits their right to advance the ball in return for an unmolested opportunity to complete the catch. The decision if, and when, to invoke that arrangement is ENTIRELY up to R.

R announces their decision to make a Fair Catch, by giving a valid signal, which by definition suggests it should be visible, timely and meet the requirements of a defined valid signal. Most officials understand that a last second signal, technically valid or invalid, may not bind a defensive player to the requirements of a valid Fair Catch, if in the judgment of that official, the defense was not given a reasonable opportunity to respond to the signal.

By rule we are required to stop play when an invalid signal has been given, even though the rule clearly states protection is no afforded. As for contact after such a signal has been given, the basic principle is simply whether the signal, which evidently did not meet the requirements of a valid FC signal, conveyed a message to the defense that a Fair Catch was intended AND was, whatever signal offered, given with enough warning that the defensive player had a reasonable opportunity to respond to it.

Splitting hairs regarding miliseconds between the catch, the whistle and the contact is not the objective. The defensive player is entitled, if not required, to contact the receiver of a kick as soon as possible AFTER the catch. The FC signal, valid or invalid, has to be clear enough to announce the intention of making a FC with enough opportunity for a defensive player, bearing down on the receiver, to recognize the signal and respond to it.

When the receiver fails to deliver a valid signal, or any signal without enough advanced warning for the defense to properly respond to it, the fault lies directly with the receiver, whose penalty may well be the contact he could have avoided by signalling properly.

I tell my BJ: On any signal, valid or invalid, there will be no return. Drop your whistle out of your mouth after the snap, therefore, no IW. (This goes for all of us.)

As for the flag, we throw it where the invalid signal is made. It may be behind the basic spot (end of the kick) if the receiver moves up a couple steps to make the catch.

I think that is 2 different subjects.

Not true, R is given an umolested opportunity to make a catch with or without a fair catch signal. That is why we have a kick catch interference rule. What the fair catch signal means is R is giving up his right to advance the ball after the catch and in return he gets protection from being hit after said catch.

Canadian Ruling
 

CANADIAN RULING:

Our equivalent to the fair catch rule designed to afford the punt receiver some protection is the Restraining Zone rule - the 5 yard halo around R.

No offside-to-the-punter K player can be inside a 5 yard halo centered at R5 when R5 first touches the ball. It's a 5 or 15 yard penalty, depending on if the ball had bounced first, and/or if the K player immediately participated in the tackle. It the descriptions above, if K was inside the 5 yard halo at the PFT, there will be a 15 yard Restraining Zone penalty applied. Result: B 1D/10 @ PFT+15.

You are technically correct MikeL, but I think you're splitting hairs, that really doesn't much matter. NF: 2.9.1 does use the language,"...under conditions in which the receiver forfeits the right to advance the ball in return for protection from being blocked or tackled by an opponent."

The point, however, was that it's the Receiver who initiates the action and is responsible to signal clearly and in such a manner that the defense can reasonably respond to the signal.