NFL Rules....
 

Talking to a guy I work with, not sure what game.

Receiver was tackled behind the LOS while a pass was in flight to him behind the LOS and no flag was thrown. Did the officials kick it or did they get it right and why?

What would be the NFHS ruling...

Canadian Ruling
 

CANADIAN RULING:

Assuming the "receiver" was a Team A member, and was tackled by a Team B member. Also assuming that the pass was a forward pass.

Defensive pass interference. Automatic first down, 10 to go, at the Previous Line of Scrimmage.

REPLY: NFHS ruling would be defensive holding. However, if (and this is a big "if") that receiver had just been involved in a fake handoff and was pretending to be the runner, withholding the flag would be proper. Probably 9 out of 10 times, the flag would be warranted.

To build on Bob M's post.... If by tackled you mean grasped and pulled down, then holding is the call. If you mean blocked and knocked to the ground, this is a legal defensive play, unless it is unnecessarily rough, or otherwise a foul, such as from behind or below the waist.