I played years of organized basketball (NJB, Jr High, HS, IMs) and was never called for a foul when raising my forearm to deny a guy trying to come through or establish position. I don't mean hitting him in the face with a shiver or something, I mean raising it about chest level. Similarly, any time a ball handler had his back turned to me, I would gain leverage with my forearm to keep him from gaining better position or getting momentum to make a move. I remember one day playing a fraternity pickup game and I did this to the guy I was guarding, a real skinny kid who had a couple inches on me. He insisted that you can only put your forearm on a guy's back for leverage if he is in the key. I know that is wrong, but are there any such restrictions in terms of space or situation? I hope this question is clear enough to understand.

And you will know MY JACKET IS GOLD when I lay my vengeance upon thee.