Changing Jerseys
 

Can a player go to his sideline, change jerseys numbers, and re-enter the game?

Yes, for instance, if they have a large amount of blood on their jersey, they may change jerseys.

Yes they can and I am assuming you are talking about changing numbers.

Canadian Ruling
 

CANADIAN RULING:

There is nothing that makes this act illegal. If a player is ejected, changes shirts, and comes back into the game, I will likely eject the head coach.

Sure. Sometimes lineman will switch to an eligible number to become the TE, or the TE will switch to a 50-79 number to meet the 5 lineman requirement. I'm sure the announcers and spotters don't like it though. ;)

We had a person at one of our association meetings state he had an issue with this based on the theory of deception. He was especially concerned due to the possibility of a player getting ejected. If they ejected player #25, they could change his jersey to #45 and the crew wouldn't know the same player returned. Many of us disagreed.

Neither does the other team. I once had a star running back change his jersey at halftime. On the first run from scrimmage the defense yelled, "He's number 44 now."