Mental health holds vary by state - don't think there's a federal provision. In California it used to be section 5150, Florida has the Baker Act. But it's generally only a short hold - whatever is in the statute, 72 hours or so. Texas has a provision for brief psychiatric emergency holds, but I'm not sure for how long. And it can involve court hearings, medication administration, etc. In the case of a federal crime, a federal criminal complaint is faster and simpler.