It's difficult to think much of an "emergency" that the president himself admits he declared just so he could get what he wants faster and without the muss and fuss of normal governing procedures. Unfortunately, President Donald Trump's declaration "that a national emergency exists at the southern border of the United States" just because neither house of Congress, under either major political party, has been impressed with his demands for funding for a border wall isn't an unheard of abuse of presidential authority.

Emergency declarations by tantrum-throwing wannabe American monarchs play a large and dangerous role in U.S. politics. In continuing that unpleasant tradition, Trump's action is less of a break from the past than a risky step toward a dictatorial future.

"Well, I got $1.4 billion. But I'm not happy with it," Trump told reporters in the Rose Garden when asked if he was declaring a national emergency just because Congress didn't give him as much funding as he wanted. "I could do the wall over a longer period of time. I didn't need to do this. But I'd rather do it much faster."

The president didn't get as much funding as he wanted? You know, in a political system designed with separation of powers and checks and balances, it's almost as if politicians frustrated by their inability to get all they desire are a feature of the system, and not a bug at all.

During the Korean War, President Truman also wanted something that wasn't his to unilaterally take—in his case, it was cheap steel for the cash-strapped government's military efforts. Subject to price controls, steel companies were disinclined to simultaneously supply that cheap steel and give wage hikes to Truman's organized-labor allies. The result was a strike—and resulting presidential attempt at nationalization "authorized" by a national emergency declaration intended as an end-run around both the normal governing process and the laws of economics.

"In order to assure the continued availability of steel and steel products during the existing emergency, it is necessary that the United States take possession of and operate the plants, facilities, and other property of the said companies as hereinafter provided," Truman insisted.

But, as the Supreme Court rapidly pointed out, "There is no statute that expressly authorizes the President to take possession of property as he did here. Nor is there any act of Congress to which our attention has been directed from which such a power can fairly be implied." The court concluded that "this seizure order cannot stand."

That the president wants something really badly doesn't mean he's entitled to make it happen. If the desired goal can't win approval through the political process, there are no grounds for making it happen at all.

That's not to say that presidents can't declare emergencies and can't act under such declarations. Just since 1979, U.S. presidents have declared national emergencies 58 times, with 31 still in effect, according to New York University's Brennan Center for Justice.

The popularity of ruling through declarations of emergency was described by USA Today as a "perpetual state of emergency" in 2014, in an article that noted that Congress had never bothered to exercise its power to review the practice.

Trump's declaration is "a patent abuse of power, and it will generate a raft of legal challenges," notes Brennan's Elizabeth Goitein. "But thanks to a lack of checks and balances in our legal system for emergency powers, the success of these challenges is not the foregone conclusion it should be." She adds that despite the limited scope of the laws allowing for emergency declarations, and judicial scrutiny, "some of these emergency laws confer extraordinary powers that are ripe for abuse, including laws that allow the president to take over or shut down communications facilities and to freeze Americans' bank accounts."

"Poorly drafted laws give the president a wide range of easily abused emergency powers," agrees Ilya Somin, a law professor at George Mason University and adjunct scholar at the Cato Institute. He believes Trump is on shaky ground in claiming emergency authority to seize private property and use military resources to build a border wall. But he cautions that "too often, courts give presidents undue deference on security and immigration issues."

By and large, most legal experts agree that the president has the authority to declare an emergency, but not to use his declaration the way he intends—probably. That uncertainty comes, again, because of traditional judicial deference to alleged national security issues and to government action overall. It's a hell of a shaky nail on which to hang your constitutional hat.

Even some members of the president's own party see problems with ruling by decree.

"No. @POTUS can't claim emergency powers for non-emergency actions whenever Congress doesn't legislate the way he wants," Rep. Justin Amash (R-Mich.) tweeted.

"When the next Democratic President declares a national emergency over gun violence and takes executive actions to curtail gun purchases, you can thank the people urging Donald Trump to do the same with regards to the border," conservative commentator Eric Erickson warned.

Nancy Pelosi, the Democratic Speaker of the House, was more than happy to suggest that's exactly where she and her allies might take matters when they're back in the White House.

"You want to talk about a national emergency? Let's talk about today, the one-year anniversary of another manifestation of the epidemic of gun violence in America. That's a national emergency," she told reporters. "Why don't you declare that emergency, Mr. President? I wish you would… But a Democratic president can do that. Democratic president can declare emergencies as well."

If you're inclined to give any politician the benefit of the doubt, maybe you could argue that Pelosi is just warning of the dangers of unilateral executive action. But she didn't raise too many objections when President Obama, from her own party, inspired news articles explaining "how a U.S. president can rule by decree."

Just as telling, then-candidate Trump was a critic of the practice at the time, asking "Why is @BarackObama constantly issuing executive orders that are major power grabs of authority?"

Now, of course, Trump is a big fan of bypassing normal governing processes to impose his will by unilateral action. If he gets away with it, be prepared for rule-by-executive-order to grow in popularity as power-mad politicians exploit a handy detour around the deliberately frustrating limitations of constitutional government.