When Sen. Rand Paul, R-Ky. said recently that he would vote against President Trump’s border national emergency declaration because he believes it is unconstitutional , many conservatives weren’t happy that the senator would defy the president.

Paul’s many critics had two primary arguments against him.

1. Trump’s declaration is constitutional because Congress passing the National Emergencies Act in 1976 makes it so.

2. We really do have a serious border crisis so prompt executive action is necessary.

Both are valid points.

Congress did pass a law 43 years ago that authorized the president to declare national emergencies, also giving him or her “the exercise of any special or extraordinary power.”

The National Emergencies Act is a statute. A statute, a law passed by Congress, does not necessarily undermine or upend the core separation of powers outlined in the Constitution.

After the Sept. 11 attacks, Congress passed an Authorization for Use of Military Force in 2001 that many Republicans believed then-President Barack Obama later abused beyond his constitutional powers concerning U.S. intervention in Libya and Syria . Conservative Republicans, including Donald Trump , certainly believed Obama was guilty of constitutional overreach in 2014 when the president protected illegal immigrants who came to America as children, so-called “Dreamers,” through an executive order. I know few conservatives who believe the 1973 Roe v. Wade decision is constitutional , despite it being the law of the land. In 2001, Congress passed the Patriot Act, yet some on the Right and Left continue to debate its constitutionality.

The Patriot Act’s constitutionality is questioned because many believe it violates the Fourth Amendment, which protects privacy and due process rights. Many still question Roe v. Wade because they believe that decision to legalize abortion nationwide circumvented the 10th Amendment and the basic constitutional principle of federalism. Many questioned Obama’s “Dreamers” executive action five years ago, not because they necessarily wanted to deport people, but they worried the president was assuming extra-constitutional powers. Many Republicans opposed Obama intervening militarily in Libya and Syria, because constitutionally, Congress is supposed to declare war, not the president on his own.

Again, a statute does not and should not necessarily turn the entire Constitution on its head. Trump’s national emergency to fund a U.S.-Mexico border is being called unconstitutional by Paul and others because it is Congress that has the power of the purse, not the president. Trump wants money for a wall that Congress won’t give him.

Nowhere in the Constitution does it say the executive branch can simply decide to become the legislative branch when things aren’t going the president’s way.

The Constitution has a separation of powers for a reason. Trump’s declaration usurps Congress’ power for himself. Or as Rep. Thomas Massie, R-Ky., Paul’s fellow Kentuckian who also opposes Trump’s executive order, put it , “There is a crisis at our border, but it’s not an emergency when Congress doesn’t spend money how the President wants.”

Yet, there is still a crisis at the U.S.-Mexico border, something Massie readily admits. The immigration system is broken. Illegal immigration is a legitimate problem.

So, why shouldn’t Trump be allowed to do something about this problem, even if it means going around Congress? This is what virtually all of Paul’s Republican critics ask.

Good question. Here are more.

Why shouldn’t a future President Elizabeth Warren be able to enact a massive carbon tax and Draconian regulations on businesses and individuals through executive order because she believes climate change represents a national emergency? Some polls show that more than 70 percent of Americans are worried about climate change.

Why wouldn’t a future President Warren enact sweeping gun control legislation in the wake of another mass shooting? Why wouldn’t she declare a national emergency to address gun violence? In the wake of these tragedies, Americans always clamor for more gun restrictions . Two in three Americans wanted to clamp down on firearms after the 2018 Parkland school shooting.

Comparatively, the highest support Trump has received for the border wall is 42 percent in January, and that was an “ all time high .”

Democrats certainly believe climate change and gun violence qualify as national emergencies. Majorities of Americans, at varying times, seem to think so too.

If future Democratic presidents agree, who are Republicans to stop them? On what grounds? Certainly not the Constitution.

Trump even raised the prospect of Democrats further abusing executive power in the future, using him as precedent, during his speech at this year’s CPAC. “They're going to do that anyway, folks,” the president said . “The best way to stop that is to make sure that I win the election.”

Don’t worry about the Constitution! Just vote for the right people!

Isn’t this precisely why we have a Constitution? To protect us at all times from the “right” or wrong people?

If you wonder why I singled out Warren as an example of what future Democrat presidents might do, it’s because she has already said she would declare these issues as national emergencies. “Oh, let’s do a list,” Warren said on the “Late Late Show with James Corden” in February. “Climate change, gun violence, student loan debt, right off the top. That’s what we ought to be working on.”

But, should any president of any party have this kind of unilateral power to enact such laws? Or should the Constitution, through its separation of powers, and checks and balances, prevent this?

Thankfully, the Constitution does prevent this. It’s the document’s primary purpose. No president, if the Constitution is followed, has this kind of power.

Right now, most Republicans are shamefully making excuses as to why the Constitution shouldn’t have such power over Trump.

Republicans who currently support Trump’s national emergency declaration regarding the border wall are using the same logic Democrats will no doubt eventually use, and currently do use, concerning their own “dire” issues.

What will Republicans say in response? "You don’t have this kind of power! Only Trump did!"

Good luck with that.

If Republicans, the supposed party of limited government, don’t mind ignoring the Constitution to get what they want in this moment, don’t be surprised when Democrats, the party of limitless government, eventually do the same.

Or instead, maybe Republicans can finally start following the Constitution? Listening to Rand Paul right now, instead of getting mad at him, would be a good start.

Jack Hunter (@jackhunter74) is a contributor to the Washington Examiner's Beltway Confidential blog. He is the former political editor of Rare.us and co-authored the 2011 book The Tea Party Goes to Washington with Sen. Rand Paul.