Any logic leaning on the nature of its legality is just turtles all the way down.
The laws were corrupted a long time ago.
Discussion
That's not a thing. The US constitution does not limit the spending type or items in any way. If Congress wants to spend money on balloon animals in the shape of a dick, and the president signs it, it's lawful. Wasteful? Absolutely. But not illicit or fraudulent at all.
Both parties signed off on this crap