Wet footballs weigh more etc. There are factors that can determine the weight of the football that happen during a game that don't have to do with inflation pressure. The guideline is to determine the TYPE of football. Its weight etc even when empty of air. Assuming they were using the right TYPE of football... the way to check the regulation during a game is with this...
No, there are two criteria: pressure and weight. The first is measured with a pressure gauge. The second requires a scale...
Now how it could be in compliance with one and not the other is a different issue.