On the recent American strike on Syria, Leeds University, UK writes:

Demonstrates Trump is willing to go it alone and conduct illegal air strikes if needed by appealing to the moral necessity to do something.

My questions are:

  1. Were the strikes legal?
  2. If they were illegal, what are the potential legal consequences? (We can ignore political consequences for this question)
  • 1
    Legal in what sense? Violation of the United Nations charter? Violation of the War Powers Act? What laws are you talking about?
    – Cicero
    Apr 7, 2017 at 15:25

3 Answers 3


The concept of "legality" presupposed a governing body, for example the US government establishes what is legal in the US, and not that is legal in Canada or Iran. There are a number of multi-national organizations such as NATO or the United Nations which include multiple countries but which are not themselves governments (and then there is the EU which actually is a kind of government built on individual countries). The most important difference between the UN and the US in this respect is that the US is a government with full power to automatically enforce its laws, but the UN does not really have "laws" or much enforcement power. There is the UN Charter and various resolutions which could be said to constitute "law", but enforcement is quite problematic.

Chapter VII of the UN Charter governs "threats to peace". Article 51 specifically says

Nothing in the present Charter shall impair the inherent right of individual or collective self-defence if an armed attack occurs against a Member of the United Nations, until the Security Council has taken measures necessary to maintain international peace and security. Measures taken by Members in the exercise of this right of self-defence shall be immediately reported to the Security Council and shall not in any way affect the authority and responsibility of the Security Council under the present Charter to take at any time such action as it deems necessary in order to maintain or restore international peace and security.

There is, however, no provision that says that a member state cannot provide humanitarian intervention against an oppressive regime, and this article can be interpreted as allowing such intervention, as in the case of the Vietnam War. Of course, if the UN passes a resolution authorizing military action then there is less of an issue. Ultimately, the matter devolves to the fact that each nation is sovereign (again, leaving aside the structure of the EU), thus any nation can legally do what it wants to, though the politics may work out that there are later consequences.

What counts as "international law" is really some set of treaties between nations, or else optional statement of guidance as to what a nation should do. The former would be enforceable within the scope of the offending nation's legal system, so if the US had a treaty with Syria prohibiting any military incursions into Syria, the US could be sued within the US legal system to enforce the treaty. There is no such treaty. In the relevant sense, I conclude that the action is "legal", even if politically unpopular.

  • Legal norms exist even if they are not enforced. So yes, "legality" can exist even if no entity exists that can dole out punishments to law breakers. Dec 15, 2017 at 21:36

Was International Law Violated?

When it used chemical weapons to kill large numbers of civilians in his own country, Assad's regime in Syria was violating its obligations under the Chemical Weapons Convention, an international treaty obligation that the regime acknowledged was binding upon it in 2013 when at U.S. insistence and with Russian supervision, the Assad regime purported to destroy its chemical weapons stockpiles.

It was also an action violating generally recognized standards of the customary international law of war that have been recognized since they were first clearly articulated in the Geneva Protocol of 1925 that took effect in 1928. This kind of action has also been recognized as a crime against humanity under customary international law, and this principle is why international criminal tribunals set up after crimes against humanity occur are not considered to be applying ex post facto laws.

Also, since early on in the Syrian Civil War, during the Obama Administration, the U.S. ceased to recognize Assad's regime as the legitimate government of Syria. According to official U.S. policy, since 2012, the Syrian National Council, and not Assad's regime, has been the legitimate government of Syria. So, rather than being an attack on a sovereign regime, this was an act in defense of a different sometimes allied regime recognized as legitimate, with whom the U.S. is not at war.

Moreover, given that fact that the U.S. now has a artillery combat ground troop unit deployed in Northern Syria as of earlier in 2017, in support of a Congressionally authorized military action in the same theater of conflict, the U.S. has a legitimate interest in protecting its own troops, as well as those of allies it supports in the part of the conflict that it is involved in under the 2001 AUMF, from chemical weapons attacks in Syria by preemptively disabling the Assad regime's ability to deploy those weapons, even though they were not directed at somewhat nearby U.S. forces in their most recent utilization this week.

So, while there may not be entirely clear international legal authorization for this particular remedy for the Assad regime's clear violation of international law, there is not a clear prohibition on doing so either, and the general rule is that sovereign states have wide discretion to take military action in support of their perceived interests, particular when violations international obligations of the offender targeted for military action provide a justification for the use of military force under international law.

This is because the main way of punishing a violation of international war while a conflict is still pending is called a reprisal which the Syrian strike fits to a tee.

A reprisal is a limited and deliberate violation of international law to punish another sovereign state that has already broken them. . . . Reprisals refer to acts which are illegal if taken alone, but become legal when adopted by one state in retaliation for the commission of an earlier illegal act by another state.

Article XII(3) of the Chemical Weapons Convention authorizes those remedies allowed under customary international law of which reprisal is one.

Did The President Have Authority To Make The Strike Under U.S. Law?

This said, the harder issue is whether this strike was legal under U.S. law, and not international law, which really has no meaningful binding enforcement mechanism other than politics, diplomacy and domestic law anyway.

While the U.S. does not recognize the Assad regime as legitimate, it is not actually at war with that regime because the Authorization for Use of Military Force (AUMF) from 2001 that has been the main legal authorization for the "war on terror" against ISIS, pretty clear does not extend to Assad's regime in Syria. ISIS has been declared to be a successor to a branch of the organization the launched the 9-11 attack upon which the AUMF declared war. But, the formerly legitimate government of Syria (Assad's regime) is very difficult to treat as coming within that definition.

However, while Congress has not authorized the use of military force by the U.S. against the Assad regime in Syria in this manner, Congress has approved appropriations to fund and support anti-Assad rebels, even though it may have been a bit of a fiasco, which at least provides some tacit evidence of Congressional consent to some sort of involvement in the Syrian civil war by the United States government against Assad's regime.

In absence of an authorization of use of military force against the Assad regime, one alternative source of legal authority to make this strike is legislation (whose constitutionality has often been questioned, but has never actually challenged, was determined by the Justice Department to be constitutional in 1980, and which is arguably not justiciable) called the War Powers Act of 1973. This Act, on its face, purports to give the President the authority to make limited use of military force for short periods of time. Specifically (per the link):

It provides that the U.S. President can send U.S. Armed Forces into action abroad only by declaration of war by Congress, "statutory authorization," or in case of "a national emergency created by attack upon the United States, its territories or possessions, or its armed forces."

The War Powers Resolution requires the President to notify Congress within 48 hours of committing armed forces to military action and forbids armed forces from remaining for more than 60 days, with a further 30-day withdrawal period, without a Congressional authorization for use of military force (AUMF) or a declaration of war by the United States.

The question of whether this incident is within the scope of the War Powers Act is disputed with U.S. Senator Rand Paul arguing the conditions triggering its use such as an attack on U.S. forces or the United States, have not been met. The issues presented by this incident under the War Powers Act are similar to those presented in the missile strike and follow up airstrikes made by the U.S. in Libya in 2011.

There is also legitimate room for dispute regarding where the authority of the President as Commander in Chief of the Armed Forces under Article II, Section 2, Clause 1 of the United States Constitution ends, and where the power of Congress to declare war and to enact other legislation pertaining to the U.S. military under Article I, Section 8 of the United States Constitution begins.

Arguably, directing U.S. forces to make an isolated military strike from a location where they are already lawfully deployed in support of an AUMF authorized military mission in the region, in exigent circumstances, against a military force that is not recognized by the United States as the legitimate government of Syria, does not constitute a true act of war and is instead merely day to day management of the operations and discipline of the United States military that is within the Commander in Chief's authority, particularly when Congress has already tentatively recognized the Syria's Assad regime is an enemy of the United States in legislation short of an authorization for use of military force.

Moreover, given that President Trump surely has majority support in both houses of Congress for this strike, the possibility that Congress may end up granting forgiveness rather than making much of the fact that he didn't ask for permission, may be mostly a formality in this case.

Generally speaking, even if this issue is justiciable (i.e. amenable to resolution through the court system), court action to enforce separation of powers questions must be authorized, at least, by a resolution of a majority of one of the two houses of Congress. Generally speaking, taxpayer standing or just plain U.S. citizen standing, does not exist to enjoin or seek a remedy from a separation of powers violation.

  • 1
    I think you are assuming that Syria really did use chemical weapons. It makes no sense to me that Assad would do that being that he was nearly winning the war anyway. It makes more sense that some other faction in Syria fighting against Assad used them in order to draw the US into the conflict. It seems interesting to me that somehow the US knew exactly where the chemical weapons came from in 1 or 2 days but never knew the whereabouts or existence of them before.
    – mark b
    Apr 7, 2017 at 17:06
  • 3
    @markb From a legal perspective, the executive branch of a sovereign nation with a military of its own is considered competent to make its own determinations of facts related to the use of military force, as is the legislative branch. A good faith belief in the facts justifying military action is generally not subject to context in any court of law. I personally don't doubt that Syria did this and find suggests to the contrary given the available evidence rather craven, but that is not a legal issue.
    – ohwilleke
    Apr 7, 2017 at 17:10
  • I'm not doubting you from a legal perspective, but keep in mind that the executive branch in the past has made 'mistakes' before - re: Yellow cake in Niger, etc. So yea, it's not a legal issue, but I highly doubt the Syrian regime did it. Much more likely a warring faction fighting Assad did it, and set them up to take the fall, knowing that the US will hop on in as they normally do. - So, I'll end the discussion as it's now political rather than legal - but I only did so because your answer actually seems to me to 'assume facts not in evidence' if you will.
    – mark b
    Apr 7, 2017 at 17:19
  • 2
    This question about assuming whether Syria did indeed use chemical weapons is an interesting one. Not because I believe they did/did not use such weapons, but because it brings the question of whether there should be some form of "trial between governments" where evidence can be brought forward. One of the pillars of most legal systems is an idea of due process, and whether or not chemical weapons were used, if we are to believe in an idea of an "international legal system", the act of firing missiles in Syria circumvents any notion of due process. Apr 7, 2017 at 17:30
  • 1
    Due process is, by and large not a concept that plays a part in the application of international law to sovereign states and subject to narrow exceptions, there are no international tribunals to which sovereign states hold themselves to be bound. Calling international law a form of "law" is not entirely accurate. It is more of a "lore" that sovereign states often use as a starting point for coming to diplomatic agreement on certain kinds of issues.
    – ohwilleke
    Apr 7, 2017 at 18:27
  1. Were the strikes legal?

Depends on the jurisdiction:

Under US Law: Probably

Under Syrian Law: Probably Not

I'm not sure about international law, If anyone would enlighten me that would be helpful.

  1. If they were illegal, what are the potential legal consequences? (We can ignore political consequences for this question)

This is a good question. If it was illegal under US law (for example, if congress passed an act that specifically forbid the supreme commander of the army (Trump) from executing air strikes on Syria) then Trump could face prosecution and impeachment.

If it was illegal under international law (say, a UN resolution, or Nato rules of engagement etc.) then there would be only political pressure. It is possible (like with the EU) that the relevant international body would pressure the US to not do such attacks again by fining them a large amount of money (as the EU does sometimes), but that is only a disincentive. Nothing bar sheer force can stop a country from doing something that it's capable of, there is only political pressure to dissuade them

  • The last paragraph would be OK on Politics.SE, but is not really helpful here: nothing but sheer force (via the police) can stop an individual from breaking any law if he is capable of it. Apr 7, 2017 at 17:23
  • Well I only meant to add that only military action can prevent future infractions (perhaps economic embargos to a lesser extent). But there are no legal remedies with regards to state-state claims apart from political pressure and occasional fine by an international body. I apologize if i was unclear Apr 7, 2017 at 17:27

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