[Hasu]

It's not like this is the first time it's ever been cold outside. The New England Patriots play a lot of football, yes? They often do so during the winter months, no?

It's exactly what you'd expect from the laws of physics, which is precisely why even if the situation you suggest is the case, the Patriots still knew that the balls would deflate due to the aforementioned extremely predictable laws of physics, and they still cheated.

If they didn't know, then incompetence is no excuse. They cheated because they didn't know about the ideal gas law? They still cheated.

[jsyedidia]

Maybe they didn't know about the ideal gas law. It seems like very few other people do. Maybe they did know about the ideal gas law and took advantage of it. In any case, they followed all the rules "to the letter", at least if you believe they did what they said they did. Most people say that when you follow all the rules, you are not "cheating".