50 U.S. Code § 1621 wrote:(a) With respect to Acts of Congress authorizing the exercise, during the period of a national emergency, of any special or extraordinary power, the President is authorized to declare such national emergency. Such proclamation shall immediately be transmitted to the Congress and published in the Federal Register.
Just so we are all on the same page with regards to the law: the Courts may not have much leeway to do anything. I'll try to give a solid explanation as to why, coming from someone with a degree in law but not specifically US law. However, most of the legal matters at hand are international in nature, in the sense that the science of interpretation is similar between nations.
So, what we have here is something I would call a 'discretionary power'. That means the President is entirely free if and when he wants to declare a national emergency. Compare that, for instance, with article I section 2 of the US Constitution:
Art. 1 Sec. 2 US Constitution wrote:4: When vacancies happen in the Representation from any State, the Executive Authority thereof shall issue Writs of Election to fill such Vacancies.
This is a bound power, meaning that when a vacancy happens, the Executive Authority must make use of that power. It has no freedom to decide. There are all kinds of laws that are inbetween. For instance:
2: The Privilege of the Writ of Habeas Corpus shall not be suspended, unless when in Cases of Rebellion or Invasion the public Safety may require it.
In this case, the privilege of Habeas Corpus may be suspended, but there is no duty to do so. However, it can only happen in case of rebellion or invasion. So, the executive is semi-bound, having a little freedom to act on its own behalf.
Now, this is important, because of the separation of powers. The judiciary can only check of Trump is acting in accordance with the law; they cannot force him to adopt a policy that is up to his discretion. Simply put: when the president has freedom to decide, the Court has very limited power to actually stop him from doing anything. In the cases above: the Courts would, for example, reinstate Habeas Corpus when there is no rebellion or invasion. However, they cannot reinstate Habeas Corpus if there is such a rebellion or invasion, because then it falls within the power of the president to decide.
Relating this to the problem at hand: if the National Emergency Act has been the following:
NOT REAL 50 U.S. Code § 1621 wrote:(a) With respect to Acts of Congress authorizing the exercise, during the period of a national emergency, of any special or extraordinary power, the President is authorized to recognise such national emergency when it occurs. Such proclamation shall immediately be transmitted to the Congress and published in the Federal Register.
The difference is: in this case, the Court can actually check if there is a factual national emergency, because the President does not have the freedom to decide what is and isn't a national emergency. He can only recognise one once it happens, and that lack of presidential power can be checked. However, the real article does not state that. It gives unrestricted power to the president to decide when there is a national emergency, so the Courts cannot actually check whether this is supported by facts.
This is a really dumb act, and it is very much open to abuse. Any law that depends on the good nature of the person it applies to is a bad law.