Opinion writer

The human body generates antibodies when it senses invasion from a harmful source. So, too, in our body politic, when a malign force such as an authoritarian executive attacks the foundation of a democracy, a healthy democracy will respond. That process of fighting a dangerous executive — President Trump — began on Friday when he declared an national emergency to justify spending that Congress had declined to authorize (a funding bill the president had signed, by the way).

The strength and diversity of antibodies fighting off Trump’s assault on democracy have been impressive.

Through the long holiday weekend, we saw hundreds of protests and rallies. We saw defenders of the president’s move grilled on television by a free and independent media while Democrats and legal experts made the case against the declaration. Anti-administration protesters gathered around the country in peaceful demonstrations, a right guaranteed by the First Amendment.

We also sixteen states band together in a lawsuit, evidence of federalism’s vitality, as well as from private groups, evidence of a robust civil society. With regard to the states’ lawsuit, the plaintiffs allege, “Contrary to the will of Congress, the president has used the pretext of a manufactured ‘crisis’ of unlawful immigration to declare a national emergency and redirect federal dollars appropriated for drug interdiction, military construction and law enforcement initiatives toward building a wall on the United States-Mexico border.”

Congress may very well file its own lawsuit, as more than 200 Democratic lawmakers have done in contesting Trump’s receipt of emoluments. (According to a CNN report, lawmakers were granted standing to sue President Barack Obama over the Affordable Care Act. “Judge Rosemary Collyer of the United States District Court for the District of Columbia held the alleged spending of public funds that had not been congressionally authorized injured Congress by nullifying its power of appropriation.”)

Many of these suits, as well as any brought by landowners whose property is taken to build the wall, are likely to make it past the first skirmishes on “standing.” Constitutional scholar Laurence Tribe tells me, “The House has standing to challenge the circumvention of its appropriations power under the district court’s holding in House v. Burwell [challenging Obamacare].” He adds, “Others with standing are those concretely injured by either the impending withdrawal of funds (as with states like California), the threatened uses of eminent domain (as with ranchers on the border) or the defamatory lies about their safety as communities (as with El Paso).”

We also can expect congressional action within the legislative branch. Joint resolutions are being introduced in both chambers. Controlled by the Democrats, the House could easily pass a declaration ending the state of emergency. And maybe a few GOP lawmakers would go along (but don’t bet on it). The Senate, under the National Emergencies Act, must then take up the resolution within 18 days and can pass it with a simple majority. The president can certainly exercise his veto, but a repudiation of his phony emergency from both the House and Senate would be as harsh a rebuke as he’s received during his time in office. We find it highly unlikely Congress could override the veto, but if the voters become exercised enough, it is always possible that enough Republicans could break with Trump.

The House already has begun to exercise another power — its oversight authority — which Republicans rarely did when they had the majority. Rep. Jerrold Nadler (D-N.Y.), the chairman of the Judiciary Committee, and his subcommittee chairs sent a letter to Trump on Friday announcing that the committee “is commencing an immediate investigation into this matter, which raises both serious constitutional and statutory issues.” The group of Democratic lawmakers continued: “We ask that you make those individuals involved in this declaration — including White House Counsel Pat Cipollone and the appropriate individuals at the Department of Justice — available to us for a hearing in the coming days so that we may fully understand both the substantive rationale and legal justification for your unilateral declarations.”

The letter’s authors also demanded answers to a series of questions such as “Did the White House seek an opinion, whether formal or informal, from the Office of Legal Counsel (OLC) before the President issued his emergency declaration?” and “What was the legal basis for your determination that (1) there is an “emergency” at the southern border and (2) a border wall is ‘necessary to support’ a ‘use of the armed forces’ at the border?”

We should not minimize the severity of Trump’s effort to destroy Democratic norms, nor his violations of the Constitution. (If the House ever gets around to considering articles of impeachment, failure “to take care the laws are faithfully executed" should be included. In the meantime, however, the array of private actions and the ability of the two other branches of government to check the executive should engender confidence. These are the signs of a still-active democracy fighting to restore itself to full health. This was the very system the Founders designed to check abuse of power.

Should Trump be denied the ability to proceed with his wall, it would be an impressive vindication of the very norms and institutions that Trump is attacking. And let’s not forget: The ultimate check remains the voters, who can send him packing in the 2020 election.

Read more:

Karen Tumulty: Branding 2020 Democrats as ‘socialist’ could be harder than Republicans think

E.J. Dionne Jr.: The real national emergency is the triviality of our politics

Dana Milbank: This Trump performance is why people talk about the 25th Amendment

The Post’s View: Trump’s make-believe crisis is untethered from truth and reality