“The opinions of judges, no less than executives and publicists, often suffer the infirmity of confusing the issue of a power's validity with the cause it is invoked to promote, of confounding the permanent executive office with its temporary occupant,” wrote the esteemed Robert Jackson in the first paragraph of the most celebrated opinion in the most famous presidential power decision in Supreme Court history. “The tendency is strong to emphasize transient results upon policies … and lose sight of enduring consequences upon the balanced power structure of our Republic,” Jackson added.

Remember these words as you analyze the legal arguments for and against the Syria strike in the coming days and weeks. Lawyers and non-lawyers alike—present company included, as much as I try otherwise—have a natural tendency to try to dress up a presidential action as “legal” if they think it accomplishes good in the world and as “illegal” if they think it doesn’t. But the question of the moral or political virtues (or not) of a particular episode of presidential unilateralism are less important than its enduring consequences for the balanced power structure of our constitution.

But how to assess these consequences? It is a remarkable fact about the U.S. Constitution that 228 years after its creation, we still don’t know what limits, if any, it imposes on unilateral presidential uses of military force. The original understanding of Congress’s power to “declare War” and the president’s power as chief Executive and “Commander in Chief” are contested. The Supreme Court has never really weighed in beyond saying, during the Civil War, that if “war be made by invasion of a foreign nation, the President is not only authorized but bound to resist force by force.” Constitutional practice over 228 years has seen a slow and steady expansion of unilateral presidential war powers, mostly (with the notable exception of the Swiss cheese War Powers Resolution) with the support or at least seeming-acquiescence of Congress, which supplied the president with a massive powerful standing military force. But the constitutional significance of this practice, while not irrelevant, is hard to fathom.

Because the constitutional script is so contested, it can be hard to assess what is new or significant in each new episode of presidential unilateralism. One way to get a sense of what is new is to look at the issue from the perspective of the executive branch lawyers who—one hopes—signed off on the legality of the Syria strike. The Executive branch, and most notably the Office of Legal Counsel, has through its legal opinions developed an elaborate set of constitutional justifications for unilateral presidential military action. These opinions are the view of one branch only, and are not the final word on constitutionality. And they construe presidential power very charitably—more charitably than many members of Congress and most scholars do, for example. But while OLC opinions are not the final word, they do provide a baseline for understanding the precedential significance of each new episode of presidential unilateralism.

Before turning to the OLC precedents, it is important to explain why last night’s strikes are different than the strikes the United States has been conducting in Syria against ISIL and al Qaeda for several years now. Though latter military actions, and the hundreds of U.S. “boots on the ground” in Syria, are all justified, from a domestic legal perspective, by the 2001 Authorization to Use Military Force. This legal justification is for many unconvincing, at least as applied to ISIL. But President Obama (and presumably President Trump) rested the attacks in Syria against ISIL on an interpretation of the 2001 AUMF and on congressional appropriations for the fight against ISIL. Whatever one thinks of these strikes in Syria, they do not stand as support for presidential unilateralism under Article II. The constitutional legality of last night’s strike against Syrian military forces in response to chemical weapon attack earlier this week, by contrast, can only be justified under Article II.

A key document for understanding OLC’s view of the legality of the Syria strike is the 2011 OLC opinion justifying the intervention in Libya. The Libya opinion clarified several lines of Executive branch precedent (many of which are collected here) and for the first time (for the Executive branch) publicly invoked the 1999 NATO intervention in Kosovo as a “precedent” (a term used in the opinion) under the Constitution for uses of force. It sets forth a two-part test for determining when a presidential use of military force abroad is consistent with the Constitution.

The first part asks whether the President has presumptive authority to use force unilaterally. For OLC, this authority turns on whether the “national interest” vindicated by the use of force sufficiently important? That sounds vague and easy to satisfy, but as we’ll see in a moment, OLC has (at least until the Syria strike) pointed to some objective limits. If the president perceives that “national interest” would be vindicated by a use of force, OLC says that he can presumptively use force abroad under his powers as “Commander in Chief and Chief Executive, for foreign and military affairs, as well as national security.”

However, OLC acknowledged “one possible constitutionally-based limit on this presidential authority to employ military force in defense of important national interests—a planned military engagement that constitutes a ‘war’ within the meaning of the Declaration of War Clause may require prior congressional authorization.” This second part of the test turns on the “anticipated nature, scope, and duration of the planned military operations.” The idea is that relatively short-term and small-scale operations abroad are not “war” and thus do not implicate the Declare War clause, but larger-scale, longer-term operations might be “war” and thus might implicate the clause.

Applying this test to Syria, consider the “scale of operations” prong first. The U.S. military last night fired 59 Tomahawk cruise missiles at the Al Shayrat airfield in Syria. We don’t know whether or when it might strike again, and for now, at least, there appears to be no prospect of directing U.S. boots on the ground toward Syrian forces. From the perspective of Executive branch precedent, air campaigns—especially short-term ones, and especially ones (like those involving cruise missiles or drones) that present practically no chance of American casualties—easily satisfy the “anticipated nature, scope and duration” test for not impinging on congressional prerogatives. (As Matt Waxman and I explained, the Obama administration’s clarification of the president’s unilateral power to engaged in “limited” war from a distance was one of its central legal legacy’s related to war powers.) As long as the military intervention in Syria is short term and limited and does not involve ground troops against Assad forces, it breaks no new legal ground.

The same cannot be said of the other prong of the test, which asks whether the President has authority to strike in the first place. What is the important national interest in intervening in Syria? No U.S. persons or property are at stake. That fact alone distinguishes most executive branch precedents. In the Libya opinion, OLC argued that “at least two national interests that the President reasonably determined were at stake here—preserving regional stability and supporting the UNSC’s credibility and effectiveness.” The second interest—the “credibility and effectiveness” of a Security Council Resolution—is a controversial basis for justifying presidential unilateralism because it seems to substitute international institutional approval for congressional approval. This line of reasoning began with Truman’s unilateral initiation of the Korean war in response to North Korea's international aggression. In that instance, in 1950, the State Department argued (among other things) that the President as Commander in Chief could deploy U.S. armed forces, consistent with the Constitution, for the purpose of upholding the “paramount United States interest” in the “continued existence of the United Nations as an effective international organization.” Moreover, the Kosovo precedent arguably extends this reasoning from the Security Council to NATO, which supported (and indeed conducted) the Kosovo strikes.

Whatever one thinks about this part of OLC’s reasoning, it at least makes presidential power turn on the consent and validation of other countries with different interests, which provides some measure of limitation, however weak. And yet even this weak limitation is missing in last night’s strikes. The President barely consulted with other countries in advance, much less got their approval through an important international security-related organization.

That leaves the Executive branch to rely on the weakest and easiest-to-satisfy of all possible interests: preservation of “regional stability” and maintenance of “peace and stability.” We can discern how the Executive branch will shape this part of the test to Syria in the President’s remarks last night:

It is in this vital national security interest of the United States to prevent and deter the spread and use of deadly chemical weapons. There can be no dispute that Syria used banned chemical weapons, violated its obligations under the Chemical Weapons Convention and ignored the urging of the U.N. Security Council. … As a result the refugee crisis continues to deepen and the region continues to destabilize, threatening the United States and its allies.

This passage contains the seeds of the Trump administration’s legal rationale for the strike. First, the administration will argue that Assad’s human rights abuses and the civil war in Syria has created regional instability that creates an important interest justifying unilateral presidential force. And second, it will argue that the United States has an important interest in deterring the spread of chemical weapons and in enforcing a norm against the use of chemical weapons. (The administration will not argue that treaties or other international law instruments related to chemical weapons authorize this use of force, but rather that the use of force is justified under the Constitution by the need to preserve the prohibitions in those treaties and related norms.)

There are at least two points to note about this rationale. First, the interests invoked—protecting regional security and in upholding or enforcing important treaty norms—will always be present when the President is considering military intervention. Taken alone—and they are all we have here—these interests provide no practical limitation on presidential power. To be sure, the regional security interest has been invoked in Libya and in many earlier OLC opinions, but they were always invoked in connection with other factors (such as the consent of the nation in question) or other more concrete and limited interests (such as the protection of U.S. persons or property, or the preservation of the U.N. Charter or a regional security treaty commitment), and never as sufficient by themselves. (The one time where these interests might have been deemed sufficient—we have no legal opinion so we don’t know for sure—is in Obama’s 2014 humanitarian intervention strike on Mt. Sinjar in Iraq. But this forgotten and under-theorized pinpoint strike against ISIL with Iraq’s consent pales in significance to last night’s massive strikes in Syria against Syrian military forces without Syria’s consent.)

Second, it seems pretty clear that the Trump team will rely heavily on Obama administration legal analysis. President Obama’s aborted threat to intervene in Syria in 2013 has led many to forgot that the administration believed it had the domestic constitutional authority to intervene without congressional authorization. Even when President Obama announced that he would seek congressional authorization for the strike, he insisted that “I have the authority to carry out this military action without specific congressional authorization.” President Obama’s Counsel, Kathryn Ruemmler, explained Obama’s legal theory in terms that dovetail perfectly with the analysis sketched above, and with President’s Trump’s words. As Charlie Savage reported:

In recent weeks, administration lawyers decided that it was within Mr. Obama’s constitutional authority to carry out a strike on Syria as well, even without permission from Congress or the Security Council, because of the “important national interests” of limiting regional instability and of enforcing the norm against using chemical weapons, Ms. Ruemmler said.

Finally, Savage’s book Power Wars reports on the existence of an unpublished “seventeen-page unsigned paper” prepared by top Obama administration lawyers that argued that the president, in a hypothetical strike in Syria, “could cite national interests in preserving regional stability, trying to impede the use or proliferation of chemical weapons, or protecting allies like Israel and Turkey.” (Savage also says the lawyers “urged [Obama] to consider going to Congress before striking Assad’s forces.”)

In sum, while it is impossible to know yet for sure, the Trump administration appears to have pushed out the OLC and other executive branch opinions and precedents to justify unilateral presidential military force based only on regional instability and the desire to uphold important international norms. As I wrote of this rationale when it was being considered by the Obama administration,

Its main problem is that it places no limit at all on the president’s ability to use significant military force unilaterally. Future presidents will easily be able to invoke regional stability and the need to protect important international norms whenever they want to intervene abroad with strikes like the one expected against Syria.

I can imagine the smile on Trump administration officials’ faces when they figured out that they would both enforce a red line that Obama wouldn’t and rely on Obama administration legal thinking to provide cover for doing so.