President Donald Trump only had to say "national emergency" to dramatically increase his executive and legal authority.

By simply uttering those words at the White House on Friday, Trump immediately unleashed dozens of statutory powers available to a president only during a state of emergency. The power of the nation's chief executive to declare such an emergency knows few strictures — it was designed that way.

For example, a fast-moving virus or pandemic may overwhelm health care resources, warranting an immediate but short-term waiver of certain federal standards, such as Medicare, Medicaid and even the privacy protections of the Health Insurance Portability and Accountability Act. President Barack Obama declared a national emergency for this purpose in response to the H1N1 influenza pandemic in 2009.

National emergency declarations are designed to be unilateral and immediate. The primary restraint on a president invoking these powers was meant to be political, not legal.

That's not to say Trump's declaration of a national emergency to build his promised wall on the United States border with Mexico won't face fights in the federal courts — it is already being challenged.

Historically, courts have shown deference to executive discretion in this area. But not always.

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When the federal courts assess whether Trump has acted beyond his legal authority, they will consider both the authority arising from congressional statutes and the president's inherent authority arising from the Constitution.

A federal court will likely first analyze whether the president had the statutory authority to act, and whether he exceeded the limits of that authority.

Congressional enactments aside, the president may claim the inherent, undisputed constitutional authority to declare an emergency and fund the wall along the southern border. A court would then apply a test dating back to a 1952 Supreme Court decision that halted President Harry Truman's attempt to nationalize the steel industry at the height of the Korean War.

According to Justice Robert Jackson's concurrence in Youngstown Sheet & Tube Co. v. Sawyer, sometimes the president asserts his independent power with no visible congressional grant or denial of that power. In this middle "zone of twilight," as Jackson described it, "congressional inertia (or) indifference" may justify the president's assertion of power.

On the other hand, if a president acts contrary to the expressed will of Congress, "his power is at its lowest ebb," the court said in the Youngstown decision. In this category, the court will only sustain the president's exercise of exclusive discretion if it determines Congress has zero control in this particular area. Although the president will usually lose in this "lowest ebb" category, a recent Supreme Court decision dealing with executive power over foreign affairs shows that sometimes, even when the executive acts at the "lowest ebb" of power, he can win.

Because Trump wields national emergency powers by virtue of saying the words "national emergency," his other words also will be scrutinized by the court in determining if he acted beyond the scope of his power. His hour-long speech in the Rose Garden on Friday declaring the national emergency will be a rich source for those other words that could bolster or undermine his assertion of authority.

At the vanguard of any challenge to Trump's declaration will be his statement: "I didn't need to do this, but I'd rather do it much faster." Even a reviewing court inclined to defer to the executive authority might penalize him for making a statement so facially contrary to the notion of a state of emergency.

Trump also missed the opportunity to insert words into the record that might have bolstered his emergency powers.

One federal statute, for example, authorizes military construction in the event of a national emergency, provided that the emergency "requires use of the armed forces" and is "necessary to support such use of the armed forces." Trump, however, did not say the words "require," "armed," or "forces" once during his lengthy speech.

On the other hand, Trump did say the word "necessary," when he said "our military has been fantastic, and I want to thank them. And it's very necessary." He also said the word "support" once, but only to say that "Sean Hannity has been a terrific, terrific supporter of what I do." Failing to satisfy the literal requirements of a statute is the kind of thing that might be noticed by a federal judge — particularly one who is a textualist, or less inclined to defer to executive authority.

As Prof. Robert Chesney of the University of Texas School of Law pointed out in the Lawfare blog, a construction project that supports the use of the armed forces might be more like a fortification than a slat fence. Trump might have drawn upon his unique take on world history, and invoked images of the Maginot Line of the 1930s — France's 900-mile "impenetrable" fortification bristling with retractable gun turrets, railways and even barracks. The Maginot "wall" was a massive, years long construction project designed to deter and defend against a German invasion. Germany ended up invading anyway — by simply driving around the wall.

Trump did not refer to a "fortification" or some other structure that might "support" the armed forces. Even some variation of the word "fort" might have helped enhance his case for "supporting" the armed forces, within the language of the law.

A court also might seize upon Trump's assertion that "last year, 70,000 Americans were killed, at least — I think the number is ridiculously low — by drugs, including meth and heroin and cocaine, Fentanyl." This could be a cause for a national emergency if drug use is an epidemic — as it has often been described. But a court might also conclude that a public health emergency is not one requiring military construction or support of armed forces.

Courts have previously considered this president's extemporaneous remarks and his stream-of-consciousness tweets in evaluating the legality of his actions, most notably in the Muslim travel ban cases. Particularly here, where the president asserts such considerable power by uttering a few words, his other words must be relevant in determining if he truly believes in his own "national emergency."