Didn't his spokesman assert it at the WH press briefings? I think they are already too deep now into legitimacy of that COLB for them to worry about that kind of caution.
It doesn't matter what others say. If it turns into a matter of law all Obama has to say is that he can't help what some well intentioned overzealous staffer did. There's going to be one low level staffer that will fall on his sword.