>> In any case, none of that will take place unless authorized by Congress, even under a declaration of war. If Congress doesn’t think it’s necessary they won’t authorize it. What civil liberties are Congress protecting by not declaring war that they don’t have direct authority to protect even with that declaration? <<
Not true. First, what I cited were instances wherein the STATES were given war powers independent of Congress.
Second, “in a manner prescribed by law” does not mean “in a manner specifically legislated after each instance of war.” Theoretically, the President could authorize quartering, citing the prescription of any laws he deems applicable, such as eminent domain. Not saying he’d do it, or that the courts wouldn’t overrule him, but why tackle these messy issues?
Lastly, even if you argue successfully that the quartering clause requires specific legislative implementation (and I’ll grant that in my court, you’d have a strong case, but AFAIK, that’s an untested assertion), the fifth amendment rights seem to be suspended by the mere existence of a state of war. (Of course, I only refer to the first sentence of the fifth amendment; the more famous second part has no qualification about wartime.)
Last I checked, arguments based on hypotheticals at the extreme reaches of the remotely possible are called “strawmen”.