In response to a potential Iranian armed retaliation following the United States’ killing of Maj. Gen. Qassem Soleimani, President Donald Trump tweeted that the U.S. military had “targeted” 52 Iranian sites “important to Iran and the Iranian culture.” Then, after near universal backlash from many in the U.S. and the international community, Trump effectively double downed on his statement, telling reporters that prior Iranian military actions against American servicemembers justified the targeting of Iranian cultural sites.

Both Defense Secretary Mark Esper and Secretary of State Mike Pompeo were forced to respond to Trump’s comments. On Monday, Esper rejected the idea, putting himself in direct contradiction of his boss. Pompeo tried to avoid answering the question directly and claimed Trump had never made such a threat. Finally, on Tuesday, Trump walked back his comments.

“You know what, if that’s what the law is, I like to obey the law,” he said, speaking to reporters in the Oval Office. “But think of it: They kill our people, they blow up our people and then we have to be very gentle with their cultural institutions. But I’m OK with it.”

This raises the question: Were 52 sites ever really targeted? Has that list changed now? Unclear. But what is clear is that: (1) international law; (2) domestic law; and (3) U.S. military law and guidance make the targeting of Iranian cultural sites illegal. There is simply no legal gray area or colorable argument to the contrary. This “legal trifecta” provides for strong protections of cultural sites around the world in both peacetime and across the spectrum of armed conflict. As Harvard Law Professor Jack Goldsmith has noted, the Uniform Code of Military Justice (UCMJ) only applies to lawful orders; unlawful orders should not be followed. Thankfully, the push back from the U.S. military and Department of Defense (DoD) leadership was quick and unambiguous.

While the issue may be currently tabled by Trump’s walk back, there are three core legal reasons why targeting Iranian cultural sites is patently unlawful and should be dismissed as an unlawful order out of hand, in case we find ourselves confronted with this again.

International Law

First, targeting Iranian cultural sites is a clear violation of international law. There is a long history here. The Civil War-era Lieber Code — a highly influential early attempt at regulating armed conflict that was issued by President Abraham Lincoln — contemplated the protection of cultural institutions such as museums, universities, and “establishments of a charitable character.” The U.S.-drafted Lieber Code undoubtedly influenced the 1907 Hague Conventions Respecting the Laws and Customs of War on Land. This treaty states that nations must take:

“all necessary steps to spare, as far as possible, buildings dedicated to religion, art, science, or charitable purposes, historic monuments, hospitals, and places where the sick and wounded are collected, provided they are not being used at the time for military purposes.”

The clearest international cultural property protections in armed conflict are found in the 1954 Hague Convention for the Protection of Cultural Property. This Convention requires “refraining from any act of hostility” directed against cultural property. Both Iran and the United States are Parties to the Convention, affording the maximum cultural property protection to both nations. Cultural property is broadly defined under the 1954 Convention to encompass

“movable or immovable property of great importance to the cultural heritage of every people such as monuments of architecture, art or history, whether religious or secular.”

To be sure, under international humanitarian law, even a protected cultural site can lose its protective status if it is used by the enemy for a military purpose. But that would be driven by actionable intelligence and facts on the ground — simply not the case here.

U.S. Domestic Law

Second, targeting Iranian cultural sites violates U.S. domestic law. The U.S. criminal code defines “war crimes” at 18 U.S.C. § 2441. It specifically references Article 27 of the 1907 Hague Convention. Article 27 states that in

“in sieges and bombardments . . . all necessary steps must be taken to spare, as far as possible, buildings dedicated to religion, art, science, or charitable purposes, historic monuments, hospitals, and places where the sick and wounded are collected, provided they are not being used at the time for military purposes.”

Failure to comply with this measure meets the explicit legal definition of a U.S. war crime.

Outside of armed conflict, there are legal protections governing the protection of cultural property ­within U.S. domestic law. As I have argued before in the Berkeley Journal of International Law, the National Historic Preservation Act already protects cultural properties both inside and outside the United States. In doing so, it implements key protections of the U.S.-ratified World Heritage Convention. While the National Historic Preservation Act and its accompanying World Heritage Convention obligations likely do not apply outside of armed conflict — the statute is silent on this — their underlying legal obligations cannot be dismissed. At a minimum, it provides a domestic legal baseline for the protection of cultural property and reaffirms our legal commitment to protect them. And U.S. courts have already upheld the law’s application to military activities overseas.

Of note, both the United States and Iran have a shared cultural property connection: Both nations have exactly 24 sites on the United Nations-protected World Heritage List.

U.S. Military Legal Obligations and Guidance

Third, targeting Iranian cultural sites violates recently updated DoD regulations and existing operational guidance. As a baseline, the U.S. military complies with the law of war “during all armed conflicts, however such conflicts are characterized, and in all other military operations.” DoD protections for cultural property were recently reaffirmed in the updated DoD Law of War Manual, which adopts the definition of “cultural property” to include property “of great importance to the cultural heritage of every people.” Cultural property protections were also reinforced in the recently updated Army and Marine Corps field manuals which makes clear that “cultural property is subject to special protections under law of armed conflict.” It makes clear that acts of hostility may not be directed against cultural property, its immediate surroundings, or appliances in use for its protection.

Further, U.S. military joint operational planning guidance takes into account environmental considerations. And each military service has complementary guidance that instructs operational commanders how to protect the environment during military operations.

In sum, military regulations and operational guidance complement and are fully aligned with existing international and domestic legal obligations mandating the protection of cultural property.

Make no mistake: striking cultural property is not just illegal, it robs all of humanity of our most precious, collective cultural heritage. We have already witnessed the horrible destruction of cultural property by both ISIL and the Taliban in recent years. The world gasped in horror at the Taliban destruction of two giant Buddha statutes in Afghanistan in 2001. The looting of Baghdad’s antiquities museum in 2003 robbed all of us of Middle Eastern history. In 2014 and 2015, ISIL caused incalculable damage and environmental sabotage in its wake in Palmyra and elsewhere.

Finally, the U.S. has often been a world leader in the protection of cultural sites around the world. Under U.S. leadership in the 1970s, the U.S. led the worldwide effort to sign the World Heritage Convention and was the first ratifying state in 1973. Congress recently created the position of coordinator for cultural heritage programs within the Pentagon’s budget. Today, the Army is working with the Smithsonian to revive “the monuments men” to advise militaries of the world on protecting cultural treasures. The U.S. military already works with the International Committee of the Red Cross and the U.S. Committee on the Blue Shield to train the military on meeting its legal obligations to protect cultural property.

The U.S. should build upon these efforts and comply with our existing legal obligations. While commentators on both sides can argue about the lawfulness and underlying wisdom of killing Soleimani, there is simply no gray legal area justifying the pre-planned targeting of Iranian cultural sites. Absolutely None.

The views expressed here are the author’s personal views and do not necessarily reflect those of the Department of Defense, the United States Navy, or any other department or agency of the United States Government.

Image: Tourists gaze upon the Gate of All Nations at the ancient Persepolis archeological site on May 30, 2014 in Persepolis, Iran. Photo by John Moore/Getty Images