Fifa president Sepp Blatter has criticised referee Steve Bennett for sending off Everton's Tim Cahill.
The Australian was shown his second yellow card after scoring the winner against Man City for lifting his shirt over his head to celebrate.
But Blatter said: "I don't agree with the referee. You should not be expelled just for pulling your shirt over your head after having scored a goal.
"If he takes off his shirt he should be off. But in other ways he should not."
Football's rule-making organization, the International Football Association Board, issued a directive in February that any player who removed a shirt to celebrate a goal
will be shown the yellow card.
Fifa said then that the rule also applied to players who bared their chest by pulling the shirt over their head, as in some countries such practice is offensive.
Fifa vice-president David Will said: "This is something I'll be raising. We have to
absolutely clarify the definition of the word 'remove' which is what is now in the laws of the game.
"We have to make it absolutely clear how that's defined - is it complete removal or is it raising it over the head?
"I think we have to accept that there is confusion and different referees are interpreting it in different ways."
Everton boss David Moyes admitted he is in the dark about the ruling.
He said: "I'm pleased Tim scored, but I don't know what the rules are when you score.
"He just pulled his shirt over his head. I'm disappointed that we lost a player for a such a soft incident."