PS3 Sticks Tournament Legal?

Since all the major tournaments are now using a PS4 for play, I was wondering if PS3 sticks were legal.

Considering the fact that you need to constantly power a PS4 pad to avoid complications, is it a known issue for a PS3 stick to cause problems due to USB slot shortages?

I’d imagine you can remedy the issue of limited USB slots by simply charging a PS4 pad via a power outlet as opposed to the PS4 itself, but I don’t know if tournaments actually bother or not since I haven’t been to one yet.