Posse Comitatus Act is bypassed by NG.
Trump will likely use National Guard first, and when it fails to enforce
his decrees he will send in the army as 'backup' when situation deteriorates(large scale revolts) and constitutional niceties are thrown out with full martial law.
https://www.abc.net.au/news/2020-06-02/can-trump-send-in-active-troops-to-stop-george-floyd-protests/12311428