Under Article 5, if one member country is attacked, all member countries may be required to respond with military force. But the U.S. Constitution says we aren't allowed to go to war without Congressional approval. If the United States of America assists another country with military force, would it be acting in violation of its Constitution?

  • 1
    Did Congress approve the North Atlantic Treaty?
    – DJohnM
    May 25, 2015 at 23:43
  • @User58220 Not the House of Representatives; they have no role in treaties.
    – cpast
    May 26, 2015 at 0:46
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    Short version: Congress has to authorize prolonger war. President has discretion to take emergency action (but needs Congress to continue them). See en.wikipedia.org/wiki/War_Powers_Resolution
    – user4012
    May 26, 2015 at 3:10
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    Even if explicit Congressional approval is not necessarily required for the US to go to war in accordance with Article 5, Congress could certainly prevent or halt such US military action: by refusing to declare war, refusing War Powers Act authorization, or cutting off funding. I don't think there's any doubt that it's in Congress's power to refuse to fulfill treaty obligations, should they so decide. Jun 4, 2015 at 1:54
  • Would "the United States of America assists another country with military force" always be considered "an Act, or Declaration, of War"? I would say, not necessarily. The "assistance" could continue for months or even years before it is considered that we have "gone to war". Aug 16, 2018 at 19:08

2 Answers 2


Short version...

  • Only Congress has the Power to declare War.
  • The military only takes orders from the President.
  • The money to run the military can only come from congress.

In effect, "Declaring War" is not a prerequisite to having a war. If congress doesn't like what the President is doing they can stop funding it (e.g., Vietnam).

In the case of NATO the congress agreed to a law by treaty that requires the President to act if Article 5 is invoked.

Details and such...

The Congress shall have Power [...] To declare War,... - U.S. Const. art. I, § 8.


The President shall be Commander in Chief of the Army and Navy of the United States, and of the Militia of the several States,... - U.S. Const. art. II, § 2.


[The President] shall have Power, by and with the Advice and Consent of the Senate, to make Treaties, provided two thirds of the Senators present concur;... - U.S. Const. art. II, § 2.

So once ratified by the Senate, the North Atlantic Treaty became part of U.S. Federal Law.

In other words, if Article 5 of the treaty is invoked, the President is legally required to respond (a "declaration of war" is not required).

Under the Constitution, a treaty, like a Federal statute, is part of the "supreme Law of the Land." Self-executing treaties, those that do not require implementing legislation, automatically become effective as domestic law immediately upon entry into force. Other treaties do not become effective as domestic law until implementing legislation is enacted, and then technically it is the legislation, not the treaty unless incorporated into the legislation, that is the law of the land.

Sometimes it is not clear on the face of a treaty whether it is self-executing or requires implementing legislation. Some treaties expressly call for implementing legislation or deal with subjects clearly requiring congressional action, such as the appropriation of funds or enactment of domestic penal provisions. The question of whether or not a treaty requires implementing legislation or is self-executing is a matter of interpretation largely by the executive branch or, less frequently, by the courts. On occasion, the Senate includes an understanding in the resolution of ratification that certain provisions are not self-executing or that the President is to exchange or deposit the instrument of ratification only after implementation legislation has been enacted.

When a treaty is deemed self-executing, it overrides any conflicting provision of the law of an individual signatory state. If a treaty is in irreconcilable conflict with a Federal law, the one executed later in time prevails, although courts generally try to harmonize domestic and international obligations whenever possible.

Source: Treaties and other International Agreements: the Role of the United States Senate (Congressional Research Service 2001)

The North Atlantic Treaty was ratified by the U.S. Senate on 21 July 1949 by a vote of 82 to 13; it entered into force on 14 August 1949.

Trivia bonus...

Article 5 has only been invoked once.

On October 2, 2001 NATO "determined that the attack against the United States on 11 September was directed from abroad and shall therefore be regarded as an action covered by Article 5 of the Washington Treaty, which states that an armed attack on one or more of the Allies in Europe or North America shall be considered an attack against them all."

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    Note that Article 5 requires no military action. A postcard with "Sorry" would technically be enough. May 27, 2015 at 23:39
  • The Article 5 because of 9/11 is still in effect, i.e. the attack is ongoing. May 27, 2015 at 23:41
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    @Philipp No. It means the President is free to act in support of other NATO states without jumping through a bunch of hoops. Congressional declarations of war are never actually required for the U.S. to wage war.
    – Rusty
    May 28, 2015 at 7:55
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    @Rusty What's the difference between declaring war and waging war?
    – moonman239
    May 30, 2015 at 17:38
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    @moonman Waging war is sending military personnel (or, these days, robots controlled by military personnel) to go somewhere and shoot people. Declaring war is formally saying "we're at war with you."
    – cpast
    Jun 1, 2015 at 2:57

The premise of the question is wrong:

Article 5
The Parties agree that an armed attack against one or more of them in Europe or North America shall be considered an attack against them all and consequently they agree that, if such an armed attack occurs, each of them, in exercise of the right of individual or collective self-defence recognised by Article 51 of the Charter of the United Nations, will assist the Party or Parties so attacked by taking forthwith, individually and in concert with the other Parties, such action as it deems necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area.
Any such armed attack and all measures taken as a result thereof shall immediately be reported to the Security Council. Such measures shall be terminated when the Security Council has taken the measures necessary to restore and maintain international peace and security.

So no country is forced to immediately surrender all military control to the Supreme Allied Commander, but will decide individually on the appropriate personal response.

THe only time Article 5 was invoked was over 9/11

On September 12th, the North Atlantic Council met again in response to the appalling attacks perpetrated yesterday against the United States.
The Council agreed that if it is determined that this attack was directed from abroad against the United States, it shall be regarded as an action covered by Article 5 of the Washington Treaty, which states that an armed attack against one or more of the Allies in Europe or North America shall be considered an attack against them all.
Article 5 of the Washington Treaty stipulates that in the event of attacks falling within its purview, each Ally will assist the Party that has been attacked by taking such action as it deems necessary. Accordingly, the United States' NATO Allies stand ready to provide the assistance that may be required as a consequence of these acts of barbarism.

For example Russia only expressed its anger and indignation and vowed to intensify their cooperation.
On the other hand the UK participated, from the beginning, in retaliatory measures in the Afghanistan War.
In the case of Germany the legal basis for participating in the Afghanistan War has to come from the Bundestag and has to be renewed every few months.
Not even the NATO as a whole is required to start battling immediately: A little over 2 months later:

The reports that NATO has been discussing sending troops, including German units, to Afghanistan as part of a peacekeeping force are unfounded.
NATO is not planning or discussing this issue in the Military Committee or any other body.

  • Do you believe that the President has the authority to make a unilateral decision to send our troops to assist NATO countries when Article 5 is invoked?
    – moonman239
    May 30, 2015 at 17:41

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