There's A Loophole In The NFL Rules That Makes Hard Hits On Kickers And Punters Illegal
According to the rulebook, kickers and punters are technically "defenseless" players at all times.
That means they can't be hit in the head or neck, and can't be blocked with a helmet-first hit, even if they are trying to make a tackle on a return. They have all the protections that a quarterback who just threw the ball has, at all times.
Here's the rule (Rules 12, Section 2, Article 4, Part G):
Article 6: Unnecessary Roughness. There shall be no unnecessary roughness. This shall include, but will not be limited to:
(...)
(g) a kicker/punter, who is standing still or fading backward after the ball has been kicked, is out of the play and must not be unnecessarily contacted by the receiving team through the end of the down or until he assumes a distinctly defensive position. However, a kicker/punter is a defenseless player through the conclusion of the down (see Article 7);
So that rule says it's unnecessary roughness to hit a kicker/punter "until he assumes a distinctly defensive position."
But another rule (12.2.7.a.6) says kickers/punters are always defenseless, meaning they can't be hit hard.
As Mike Florio of Pro Football Talk noted, it'd technically be a penalty for a returner to ram head-first into a punter who was trying to tackle him.
The defenseless player rule outlaws "unnecessary contact" in situations where players with the ball are hung out to dry - punt returners making a catch, a receiver jumping for pass over the middle, a quarterback who just made a throw, etc.
It wasn't intended to protect players who are actively trying to make a tackle.
One of the biggest hits of the year was delivered by Colts punter Pat McAfee. He was technically "defenseless" on this play:
Clearly the Huber hit (below) should be illegal. You can't have guys getting blindsided by hits to the head, regardless of which position they play.
But the putting a blanket "defenseless" tag on kickers and punters at all times seems overly broad.