[swebs]

I don't see any mention of that

https://www.archives.gov/founding-docs/constitution-transcri...

[chrisseaton]

I think it's called the Posse Comitatus act or something like that.

[swebs]

It looks like that specifically forbids them from enforcing the law, not public works projects. And there seem to be several exemptions.

https://en.wikipedia.org/wiki/Posse_Comitatus_Act