"Legit war time measures" is not a thing. If Congress declares war on Cuba or Venezuale for example, people who do not support it will not see the measures as "legit". The US has a lot of precedent of bombing/invading other countries at the whim of presidents without actually calling it a war for decades.
And for better or worse, it is actually good that it is like this. Otherwise, if Congress declares war on Iran or China or whatever, the whole country will be put on a war footing, companies will be directed to build whatever the Pentagon says it needs, drafts will be enforced and so on. And it would be pretty ugly.
if you didn't notice we are talking about wwii
usa was not aggressor
fat chance congress declaring war of aggression on a peaceful country
If Congress declared an actual war and if they declared to use war time laws to force a private company to comply with the war effort, we wouldn't be having this conversation.
What happened was different: a private company decided to enforce some terms, as they can do during peace time and they have been bullied in a way that is disgraceful precisely because it didn't happen during war time nor it has been done using the existing laws around that.
What is the purpose of having laws in the first place if we accept that the government can rule by intimidation?