Well, once again, I'm not a lawyer so, I've relied on the only legal products of this question. The 2002 memorandum that studied the issue and determined it would not be torture as defined in any body of law having jurisdiction over the application of this technique by the U.S. against detainees. And, the 2004 revision of that conclusion that said the same thing.
I would also point to the fact there is no subsequent court ruling on the specific question of whether or not the technique, as applied by the Bush administration, violated any laws.
A reasonable people could conclude that, although there are a bunch of pissed off people that didn't like the fact we were waterboarding terrorists and tried their best to have it prosecuted as a crime, no one was confident enough in that proposition to actually try the case in a court.