Edit: I should add, it would be under the CFAA.
Edit #2: I could be wrong, it looks like they used Parler's APIs, and didn't bypass any auth. I really shouldn't have even called this a hack, it's more just archiving. But weev went to jail for the same thing, so I'd say there's a chance of prosecution, would come down to a court case. If I was the person who did this, I would never step foot in America, just to be safe.