Well, they will let him play, but will suggest that he'd likely not have a good time because he doesn't have an AEG. But is all part of the learning experience. I remember my first game, was only 4 vs. 4, I only got two kills all day annd got shot a lot. Mind you I only used an AEG all afternoon, and my M11 and M24 in the morning, but still.........
Wil86, go to Canadian Tire and pick up the tri shot Crosman shotgun. It's a springer, has some decent power to it, and is only $120 (unless on sale). Buy a bag of good BBs, say 0.25g minimum, and go play. You won't do well with it since it'll be your first time (not saying you'll do well with an AEG either, it's the way you absorb what is going on, it'll all spin around you and you'll get confused by everything), but you'll learn some valuable lessons with it. I have that shotgun and will be using it as much as I can this year, I plan to give my AEGs a rest this year.