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I don’t see how it weakens Trump’s Position. He has the Authority under the Emergency act.
Then there are official statements by Both Party’s Leaders both in Congress and outside it where they admit it is a problem. Going back Decades...they have failed to deal with it causing it to get worse and put American Lives at risk. Specificly Hillary, Bill Clinton’s SOTU speeches, B.O. Speeches, Chuckles the Clown Schumer’s House and Senate Speeches.
They failed to deal with it.
In the sense that the act of Congress allowing a declaration of an emergency is an indication of the mind of the Congress in light of Constitutional restrictions.
If the Congress can convince the court that this declaration is not what they intended, that would weaken POTUS' position. I am not a legal beagle and have no idea how that will fall out.