With the focus on Syria calming over the past couple of weeks due to the advent of a deal between the U.S. and Russia to allow Syria to give up their chemical weapons, contemplation on other issues related to the Syrian civil war is in order.

The Washington Post a few weeks ago reported on a very interesting maritime security element related to the Syria story – the shipping of arms from Russian and Russian controlled ports in Ukraine to Syria. Commenting on a report published by C4ADS, the Post provides an intriguing story on how the Russians have been supplying Assad with shipments of arms – such as tanks, helicopters, and rocket launchers. Also, if you haven’t already, please read the excellent commentary on this issue written by LCDR Mark Munson. Notwithstanding any deal regarding chemical weapons, the arms shipments that help sustain the Assad regime will continue to obstruct a sustainable peace in the conflict and in the region. This maritime security issue provides an opportunity for decision makers to explore creative solutions. Any discussion on how to dismantle the arms trade, however, would be lacking imagination if it did not include the classic naval blockade.

From the Royal Navy’s blockade of Cadiz in 1797 to Israel’s blockade of Gaza in 2009, a blockade is a time-tested method. An important consideration if the U.S. were to blockade Syria, however, is that a blockade is generally considered an act of war. Because President Obama and most of the U.S. population have an unfavorable view of war with Syria, history may be able to provide an alternative.

In July 2013, the Department of Justice released a cache of old Office of Legal Counsel (OLC) memos from 1933-1937. As a brief introduction, OLC provides the President and others in the Executive authoritative legal opinions, many of constitutional relevance. This office is most famous recently for producing the torture memos of the Bush administration. One of the little gems hidden in the stack of memorandum opinions titled “Authority of the President to Blockade Cuba.” Interestingly, this opinion was dated January 25, 1961, almost 22 months before the Cuban Missile Crisis. Nevertheless, the OLC memorandum opinion provides an interpretation of international law that would apply even today if the U.S. Navy was to blockade Syria. The memorandum opinion states:

“At the outset it should be noted that both courts and commentators are agreed that a blockade involves a state of war; i.e., it is the right of a belligerent alone…The United States is not in a state of war with Cuba in the traditional sense….Accordingly, the principles of international law, as presently developed and followed by the United States, would seem to furnish no legal justification for the imposition by this government of a blockade of Cuba.”

Simply exchanging “Cuba” with “Syria” would suggest that a blockade to stop the arms flowing in from Russia would be illegal under international law – unless the U.S. is willing to go to war with Syria. However, the memorandum provides a potential alternative to justifying a blockade:

“In this posture, we turn to the question whether it is, nevertheless, possible to argue that a blockade of Cuba is justifiable. That the United States is engaged in a “cold war” with major communist nations and with Cuba is plain. To keep communist imperialism from engulfing the United States is a matter of vital national interest.”

The memorandum further explains by quoting Doris Graber:

“Interventions undertaken to further these interests were lawful if those who authorized them believed that intervention was a last re-sort to safeguard the nation from extreme peril and proper means of intervention were used. . . .”

Doris A. Graber, Crisis Diplomacy: A History of U.S. Intervention Policies and Practices 211–12 (1959).”

So, put another way, it seems as if the existence of the “cold war” was sufficient to allow the U.S. to intervene and blockade Cuba.

What does this mean in the Syria context? If decision makers were to seriously consider legally blockading Syria to prevent support to the Assad regime, they would be required to meet the following:

a. Analogize the “cold war” with the “war on terror” (which commentators have done in the past),
b. Fit the civil war in Syria into the global war on terror, and
c. Strengthen the connection between intervention in Syria with “safeguarding [this nation or our allies] from extreme peril.

If decision-makers can successfully meet these three requirements, then the U.S. could potentially be legally justified in unilaterally blockading Syria. This, however, doesn’t mean that it would be prudent or feasible to do so.

LT Dennis Harbin is a surface warfare officer and is enrolled at Penn State Law in the Navy’s Law Education Program. The opinions and views expressed in this post are his alone and are presented in his personal capacity. They do not necessarily represent the views of U.S. Department of Defense or the U.S. Navy. This article is for informational purposes only and not for the purpose of providing legal advice.