The problem with "Any Lawful Use" is that the DoD can essentially make that up. They can have an attorney draft a memo and put it in a drawer. The memo can say pretty much anything is legal - there is no judicial or external review outside the executive. If they are caught doing $illegal_thing, they then just need to point the memo. And we've seen this happen numerous times.
Its interesting to see the parties flip in real time. The Democrats seem to be realizing why a small federal government is so important, a fact that for quite a few years their were on the other side of.