Russian President Vladimir Putin and Iranian President Hassan Rouhani meet during the BRICS/SCO Summits – Russia 2015 on July 09, 2015 in Ufa, Russia. (Photo by Alexey Filippov/Host Photo Agency/Ria Novosti via Getty Images)

The Trump administration is considering “whether to make confronting Iran an explicit new goal for the more than 2,000 American forces currently in Syria,” according to a recent report by the Wall Street Journal.  If a policy of military confrontation with Iran in Syria is actually on the table, this is troubling on several levels.

As I’ve argued here, there are many reasons to avoid an escalation of fighting in the devastating conflicts in Syria.  Moreover, a policy of purposeful military confrontation against Iran begs for a broader regional conflagration that could be exceedingly difficult to contain.  The risks of accidental confrontation are already high, and the consequences of a hot conflict could be dire for civilians caught in the middle and for U.S. national security interests – the very real possibility of retaliation against U.S. troops in Iraq is but one of them.

Beyond these potential policy and humanitarian consequences, there are fundamental legal ones:  it is hard to see how seeking out a military confrontation with Iran in Syria for the purpose of preventing Iran “from cementing its military presence in Syria or establishing a secure route across the country,” as the WSJ article suggests, would be lawful.  To be sure, if the United States or another state (such as Israel) is subject to an armed attack by Iranian forces or there is an imminent threat of armed attack, necessary and proportionate force may be used to achieve legitimate self-defense aims.  But we should also be clear that the pre-emptive use of military force in an effort to curb Iranian influence would not be a valid exercise of self-defense – international law does not permit states to spoil for a fight.

As a domestic law matter, such action would not be congressionally authorized by either the 2001 or 2002 Authorizations for Use of Military Force (AUMFs).  Nor, I suspect, would anyone seriously argue that seeking out a military confrontation with Iran in Syria would be a valid exercise of the President’s authority in Article II of the Constitution.  In sum, proactively shifting the mission of U.S. troops in Syria to countering Iran – absent an armed attack or imminent threat thereof – would mean shifting from the thin ice the United States is already on in Syria and plunging into sending troops into harm’s way without a valid legal basis for doing so.

To understand why, let’s take a brief look at the administration’s legal rationale for its actions in Syria to date with a focus on uses of force against the Syrian government and what the administration calls “pro-Syrian government forces” (which includes Iran).

The Current Legal Basis for U.S. Military Action in Syria

In June, during an escalating series of military confrontations between the United States and the Syrian regime and its allies near At Tanf, Syria, I raised the following three questions about the international and domestic legal bases for these actions:

[Under international law,] is taking and holding Syrian territory sought by the Syrian regime and its allies lawful?  And if so, what are the limits of action the United States can take against pro-regime forces under its theory of self-defense against ISIL?  As a domestic law matter, has Congress authorized the use of force against the Syrian regime, its allies Russia and Iran, and their non-state proxies, or is the Trump Administration acting unilaterally?

It’s now clear that the administration believes the answer to the first question is yes, at least when there is a particular type of nexus to the counter-ISIS fight.  The administration’s June 2017 and December 2017 supplemental consolidated reports to Congress submitted under the War Powers Resolution describe military actions against the Syrian regime and its allies as “lawful measures to counter immediate threats to the United States and partner forces engaged in [the counter-ISIS] campaign.”  The Administration provided a more fulsome explanation of its legal basis for these actions in August, in a State Department letter responding to questions raised by Senate Foreign Relations Committee Chairman Bob Corker.

Based on the State Department letter, the argument goes like this:  the United States and its partners are acting in individual and collective self-defense against ISIS.  The Syrian government is “unable or unwilling” to effectively confront the threat posed by ISIS to Iraq and other states, and thus the United States and its partners may take “necessary and proportionate actions in Syria against ISIS” without Syrian government consent.  Furthermore, the argument goes, it is both necessary and proportionate in the exercise of self-defense against ISIS to “use force to defend U.S., Coalition, and U.S.-supported partner forces from threats by Syrian Government and pro-Syrian Government forces.”  The letter does not address the so-called “deconfliction zones” the United States and its partners have created in Syria, but presumably the argument is that creating territorial zones within Syria from which the United States and its partners may use force to expel all comers, including the Syrian government and its allies, is also necessary and proportionate in the exercise of self-defense against ISIS.

That last proposition begins to answer the second question – what are the limits of the United States’ self-defense theory in Syria?  No outer boundary has been articulated publicly by the administration to date.  But looking at the practice on the ground of creating and defending territorial zones against even the Syrian government, the logical conclusion is that the administration believes the United States and its partners have a tremendous amount of leeway vis-à-vis the Syrian government (and its allies) once an “unable or unwilling” determination is made.  (Indeed, without further explanation by the administration as to why it believes creating these zones is a necessary and proportionate means of addressing the ISIS threat, it is difficult to see how these activities reflect the law of self-defense.)

The third, domestic law question follows naturally from the international law analysis.  As Professor Ryan Goodman has explained, if you accept the self-defense argument described above, and the domestic law argument that the 2001 AUMF extends to ISIS (a big if), it is not a logical stretch to argue that as a domestic law matter the 2001 AUMF also authorizes uses of force against those who threaten U.S. and partner forces in the context of conducting counter-ISIS operations.

Switching the Mission to Confronting Iran

No matter which side of the divide you fall on with respect to whether the law of self-defense is capacious enough to provide international legal authority for current U.S. actions in Syria, it should be clear that further shifting the mission of U.S. forces in Syria to “confronting” Iran in order to prevent it from “cementing its military presence” (not responding to an armed attack or imminent threat thereof) would not be a valid exercise of self-defense.  The exceptions to the prohibition on the use of force are authorization by the U.N. Security Council acting under Chapter VII of the U.N. Charter and self-defense in the event of an actual or imminent armed attack.  Notably, if there were to be an imminent threat of armed attack that did justify the use of force in self-defense, the motives expressed by some senior administration officials who seem to be spoiling for a fight could make it harder to believe a self-defense argument were being made in good faith.

Under domestic law, with no real nexus to the counter-ISIS fight, there is no serious argument that the 2001 or 2002 AUMFs would provide domestic legal grounding for such a mission.  And as noted above, it’s hard to see a strong argument that seeking a military confrontation with Iran in order to curb its influence in Syria would be a valid exercise of the President’s unilateral Article II authority.

In these circumstances, if a mission of countering Iranian influence is developed for the U.S. military in Syria, there could be significant rule of law consequences.  U.S. credibility when we send our forces into harm’s way abroad depends on our ability to explain that we are acting lawfully, and to do so in a manner that won’t strain credulity among our international partners.  There could be long-term consequences to U.S. credibility, and to the rule of law on the international plane, if we put our uniformed personnel in a situation where that is clearly not the case.

Finally, given the facts as we understand them, there remains one more important question – are the policymakers in the Trump administration bringing their lawyers into the discussion at the early stages of formulating policy options?  It’s hard to know while the policymaking process is still underway, and it is appropriate that any legal advice offered during that process be discussed in confidence.  In any event, the talent, dedication, experience, and integrity of career lawyers at the Departments of Defense, State, and Justice should be marshalled early on in these discussions and their advice heeded.  And if a decision is made to shift the mission of U.S. forces in Syria, the legal arguments on which U.S. military action relies should be publicly explained.