[jacobwg]

I think not in that the proclamation states that the flag should be lowered "at the White House and upon all public buildings and grounds, at all military posts and naval stations, and on all naval vessels of the Federal Government in the District of Columbia and throughout the United States and its Territories and possessions" and "at all United States embassies, legations, consular offices, and other facilities abroad, including all military facilities and naval vessels and stations".

So, for those locations it seems mandatory. But the flag code that states things like that state flags should be flown lower that the federal flag is codified tradition and not law, so technically states do not have to follow, as far as I understand.