What the heck does this have to do with the U.S.? I'm just saying hypothetically if I had a clothing brand called "Freak3y Clothing" and Wayne Odesnik(who I hate) shows up at the US Open wearing my clothing, that wouldn't be allowed? I'm not saying anyone hates Tommy(he's one of my fav players), but I'm pretty sure you have to be sponsored by a company to go on TV wearing their clothing. Otherwise wouldn't Baghdatis start using an actual brand of racket instead of his blank one?
Those brands you are speaking of make commercial clothing articles as well. Endorsing other professional tennis players does not change that.