Go back a second here. Of course they are constantly evaluating if they are within the law; so is every other person when filing their goddamn taxes. But legal questions of the magnitude of "do we have the right to collect this data under the constitution" are obviously not decided on the spur of the moment. When the CIA wanted to torture, they asked the DOJ and John Yoo to come up with a piece of paper telling them in lots of legalese that they were allowed to do so.

Obviously these legal interpretations exist, today.