Where does the buck stop?

[Gelston]

While that might be a workable loophole, if anything goes wrong in the near future that those funds could (should) have been used for instead, it amounts to political suicide. You drain disaster relief to build a wall for a divisive issue and Katrina II hits or something, you're pretty much done.

I think that's something they'll steer clear of.

Nah. If anything goes wrong in the future, Congress will approve more funds, or they'll look like assholes. They might talk shit and say Trump took it, but they aren't going to say no to approving more cash for disaster relief.