Breaking down the call on the Bucs' final play
Stephen F Holder, The St.Petersburg Times, published 22 October 2012

Many remain confused about the application of the rules on the games final play. Heres an attempt to clarify things. When cornerback Patrick Robinson clearly pushed Mike Williams out of the back of the end zone Williams was called for illegal touching as a result and his tying touchdown was negated it was deemed a legal play.

Why? Because, under long-standing NFL rules, aggressive contact is permitted by defenders against receivers after a quarterback leaves the pocket. The officials determined that Josh Freeman had already left the pocket when Robinson shoved Williams.

Many have asked about the notion that Williams can re-establish position and then make the catch. That, however, only applies when the receiver is pushed out of bounds as the result of an illegal act (like illegal contact). Heres what the NFL rule book says on that topic:

If an eligible receiver is forced out of bounds by a foul by a defender, including illegal contact, defensive holding, or defensive pass interference, he will become eligible to legally touch the pass (without prior touching by another eligible receiver or defender) as soon as he re-establishes himself inbounds with both feet or with any part of his body other than his hands. See Article 8, Note 3.

That does not apply here, so with no other caveat, its illegal touching by Williams, and the call would be correct. Before you ask, here's why this rule exists: Because once a quarterback leaves the pocket, he is considered a runner. A receiver, while still eligible, could easily become a blocker. Agree or disagree, this rule enables defenders to counter that.