Your problem is that the stadia are not public places but private property. This means that the owners of said property are in a position to make up whatever rules they fancy and apply them regardless of how mean spirited they appear.

With my cynical head on (the one that I use all the time that is...

) I suspect that the clubs that own these stadia are frightened that you might make some money out of the pictures that they haven't managed to grab a share of. It's all about corporate image and copyright I'm afraid.

Whether an athletics stadium is likely to take the same approach I couldn't say. Perhaps your best bet is to contact them and see what their official approach is. It may be open house or you may need to explain to them what you are intending. Sometimes all that's needed is the courtesy of asking permission and advising who you are, what you wish to do and why...