On Sunday, Sen. Rand Paul announced what appears to be the decisive vote cementing a Senate majority for a joint resolution to overturn President Donald Trump’s declaration of a national emergency on our southern border.* That joint resolution, which passed the House 245–182 on Tuesday, might be mistaken as but another element of theater in an interbranch funding fight staged with greater regard for the demands of drama than the niceties of law. Trump started it with an emergency proclamation that is less relevant to actual wall construction than it sounds. Much of the funding Trump wants, if obtainable, would have been available with or without his pronouncement. If that is so, it seems a fair question whether the joint resolution, if enacted, would really tighten the spigot in any event and whether the effort is worth it given the certainty of a Trump veto. The answer is that, yes, it is.

Under the 1976 National Emergencies Act, the strictly legal function of a declaration of emergency is to trigger the president’s access to a host of existing legal powers that come into play only after such a declaration is signed. From the chief executive’s point of view, these national emergency statutes are like special recipes that a president may cook only after he formally announces, “I’m hungry!”*

Yet when the White House revealed its intended sources of wall funding, the list looked oddly fishy. For one, $1.375 billion would supposedly come from the Homeland Security appropriations bill, which is weird, given that this particular appropriation cannot be used for new wall construction. And an additional $6.1 billion would supposedly come from the Treasury Department’s forfeiture fund, the Department of Defense’s drug interdiction program, and the Department of Defense’s military construction account. Of those three remaining pots of money, only one—the military construction account—is actually triggered by the president’s emergency declaration. The other two are not special recipes. They are part of the everyday bureaucratic buffet.

What reading the law thus strongly suggests is that the point of the declaration was not to accelerate wall construction.

Thus the only way in which the declaration potentially opened up wall funding that would not otherwise exist is through the emergency-triggered statute that loosens up the Defense Department military construction account. That potential, however, is just a chimera. Under the relevant statute, “military construction” must involve “a military installation,” which the act defines as “a base, camp, post, station, yard, center, or other activity under the jurisdiction of the Secretary of a military department.” It is a great first-year law school problem to ask whether the proposed border wall fits within the terms, “a base, camp, post, station, yard, center, or other activity.” (I know because I assigned it to my students a couple of weeks ago.) But even if the wall could be justified as “other activity,” it would not be “under the jurisdiction of the Secretary of a military department,” but rather under the Secretary of Homeland Security, which is a civilian agency. In other words, the statute unambiguously should not permit the Defense Secretary to shift money toward building a wall for and under the jurisdiction of a civilian law enforcement operation.

What reading the law thus strongly suggests is that the point of the declaration was not to accelerate wall construction. The point was to make sure that the day’s news narrative was not dominated by “Trump caves on appropriations bill.”

But if Trump’s emergency declaration was actually less important legally than it seems, the joint resolution is actually more important for three reasons. First, the courts will face the wall dispute largely as the kind of statutory interpretation fight that makes nonlawyers glad they never sat through law school. Their focus will be deciding whether the complex clauses of the statutes Trump would invoke do or do not convey the discretion he seeks to move money around.

In contrast, the joint resolution underscores the big-picture constitutional dimension of the fight. Congress’ power of the purse is its heavy artillery in the scheme of checks and balances. The Constitution underscores its significance through redundancy. Not only does Article I vest the spending power in the legislative branch, but a separate provision bars the executive branch from spending money unless appropriated. If presidents can find ways to work around Congress’ rejection of their requested spending priorities, Congress’ big gun has been silenced.

Second, the joint resolution, if enacted, will be a signal to future presidents. Harold Bruff, whose book Untrodden Ground is a superb review of how presidents from Washington on have interpreted the Constitution, writes: “Presidents find guidance and comfort in what their predecessors have done successfully and are comfortable asserting the legality of present action based on prior action.” If a majority of Congress rejects Trump’s national emergency, future presidents are less likely to regard his declaration as a legitimating precedent for their own unilateralism.

Third, the joint resolution could actually affect how courts address the technical statutory issues ahead. For example, using Defense Department funds under its authority to give support for counterdrug activities depends on whether the border wall is an acceptable use of statutory authority to construct “roads and fences and installation of lighting to block drug smuggling corridors.” A wall across the entire border sounds as if it might be more than a “fence” and blocking more than a “corridor.” A joint resolution underscoring that Congress has deliberately rejected the inclusion of border wall fencing in response to a presidential request could well move a court to say that this statute will not help finance it.

The Treasury’s Forfeiture Fund offers an even more complicated statute to parse. A lot of the statute describes specific purposes for which money in the fund may be spent. But the statute also enacts an ongoing appropriation of money from the fund to be allocated to that list of purposes. If one reads just the appropriations part of the statute, the Treasury’s powers seem extremely broad: “[U]nobligated balances … shall be available … for obligation or expenditure in connection with the law enforcement activities of any Federal agency.” That sounds as if funding the border wall would be OK. If, however, the seemingly unbounded reference to “law enforcement activities” encompasses only the specific activities cataloged in the earlier sections, it is not at all clear that Homeland Security’s border wall construction could be covered. Again, a majority vote for the joint resolution could help put the judiciary in a skeptical mood.

In short, a majority vote in both the House and Senate rejecting the national emergency might well be significant both now and in the future. It would plant a flag for checks and balances, reduce the likelihood of future abuses, and strengthen the technical legal arguments against wall funding. Most of all, it would remind our most swaggering chief executive that even a president with a veto power doesn’t always get the last word.

Update, March 4, 2019: This post has been updated in these two places because of news developments and for clarity.