Michael KreponSenator Rubio and Kim Jong Un Weigh In on the CTBT

In rapid succession, the Senate Foreign Relations Committee convened its first Hearing on the Comprehensive Test Ban Treaty in seventeen years, and Senator Marco Rubio and 32 Republican colleagues made public a letter to President Barack Obama opposing the administration’s UN Security Council resolution and a companion P-5 statement reaffirming the CTBT.

Senator Rubio & Co. threatened retaliation by denying U.S. funding for the Treaty Organization’s International Monitoring System. Then, Kim Jong Un weighed in with another nuclear test explosion.

The Rubio letter argued that funding for the IMS is not needed because U.S. monitoring capabilities (“National Technical Means”) are superior. This is only half true. U.S. capabilities are, indeed, superior, but they are also secret, and thus rarely helpful in compliance controversies. Administrations are loath to declassify data because doing so could provide indications of detection capabilities.

The CTBTO’s parallel monitoring system has the major advantage of being an extremely hard-to-rebut public network. All member states have access to data collected. Based on IMS data, everyone can, for example, assess the yields and implications of North Korean testing. Thus, the value of IMS data is far greater when a state seeks to test covertly. Moreover, the release of data and their evaluation by member states could trigger on-site inspections — but only with the Treaty’s entry into force. The Rubio letter therefore places those who worry most about covert, extremely low-yield Russian and Chinese tests in the awkward position of being against their detection and effective prosecution.

After being treated as a backwater for the first seven and one-half years of the Obama Administration, the Treaty’s central object and purpose of banning nuclear explosive testing is now very much on the front burner, awaiting reaffirmation by the P-5 and the Security Council. As a result of this belated effort, four important developments have come to light.

First, the George W. Bush administration sought to establish grounds for the United States to shed the obligation under customary international law to respect the object and purpose of the CTBT pending its entry into force. The Bush Administration never publicly revealed its intent to do so.

Second, State Department lawyers appear to have conceded the point that the Bush Administration’s actions may have been sufficient to release the United States from its obligation under customary international law to respect the object and purpose of the CTBT pending its entry into force.

Third, the Obama Administration’s statements of support for the CTBT – to be clarified further by the forthcoming UNSC resolution and P-5 statement – have emphatically re-imposed U.S. obligations under customary international law to adhere to the object and purpose of the Treaty pending its entry into force.

And four, hard-core Treaty opponents reject the Executive Branch’s authority to reimpose this established principle of international law, unless and until the Senate provides its consent to ratification — and certainly not after the Senate has refused to provide its consent.

All of this was news to me until two weeks ago. For chapter and verse, check out the SFRC Hearing and Senator Rubio’s letter.

Article XVIII of the Vienna Convention (signed, but not ratified by the United States and, after 36 years, widely accepted as customary international law), reads as follows:

“A State is obliged to refrain from acts which would defeat the object and purpose of a treaty when:

“It has signed the treaty or has exchanged instruments constituting the treaty subject to ratification, acceptance or approval, until it shall have made its intention clear not to become a party to the treaty; or

“It has expressed its consent to be bound by the treaty, pending the entry into force of the treaty and provided that such entry into force is not unduly delayed.”

CTBT critics have turned these obligations upside down. As Stephen Rademaker testified before the SFRC,

“[T]here is a serious question whether the Senate accepts, or should accept, the notion that the United States has an obligation under international law “to refrain from acts which would defeat the object and purpose” of any treaty that the President has signed but the Senate has not yet approved.”

(Steve’s elaboration can be found here.)

Steve’s interpretation of international treaty law resonated with some members of the Foreign Relations Committee. Senator Jim Risch, the Committee’s Ranking Majority Member, minced no words on this subject:

“What customary international law binds me, as a United States Senator? I am not responsible to anyone except the people of America and the courts of America, not to … customary international law. That is nonsense, absolute nonsense, for us as Americans, … members of a sovereign, free, nation on the face of this planet. No, I don’t have a gripe with [customary international law], I absolutely reject it.”

Senator Rubio previewed the letter he subsequently released with these remarks:

“[T]he simple signature by our President, in our system under our sovereign constitutional system, does not in and of itself enter us into anything until it is affirmatively ratified. Otherwise, what’s the purpose of the constitution? At that point, basically the president can bind us under “customary international law” anytime he or she signs onto any document in the world, irrespective of whether Congress acts or doesn’t, and if Congress chooses to approve it, well that’s a nice touch.”

In this view, U.S. obligations under the CTBT lapsed when the Senate refused to consent to ratification in 1999, and when President George W. Bush’s Administration made public declarations opposing the Treaty, most clearly affirmed to the SFRC in a letter by Secretary of State Condoleezza Rice to Senator Jon Kyl in 2008.

These actions are notably different from, and do not meet the standards set by the Bush Administration when announcing it had no intention of seeking ratification of the Rome Statute establishing the International Criminal Court, thereby freeing the United States of any obligation “to refrain from acts which would defeat the object and purpose” of this international agreement. In this instance, the Bush administration publicly renounced U.S. participation and sent a letter to the Secretary General of the United Nations to this explicit effect. This accord was formally removed from the Senate’s Executive Calendar. In contrast, the Bush Administration sent no such letter to the Secretary General, and never explicitly and publicly stated that it was henceforth free of obligations under Article XVIII of the Vienna Convention with regarding nuclear testing. The CTBT remains on the Senate’s Executive Calendar to this day.

The most plausible explanation of why the Bush Administration chose not to forthrightly announce that the United States was freeing itself of any obligations to respect the object and purpose of the CTBT, including transmitting a letter to this effect to the UN Secretary General, was that this would have prompted firestorms of domestic and international protest. In addition, the Bush Administration, which wasn’t planning to resume testing, did not wish to open this door for others. So, the inferences of the Administration’s opposition to the CTBT were left unsaid.

Nonetheless, the State Department’s lawyers might be willing to concede that the Bush Administration met the blurry standard of what it takes to walk away from treaty obligations. The Administration argues that this point is moot, in any event, because President Obama has clarified support for the CTBT, thereby recommitting the United States to its Article XVIII obligations not to defeat the object and purpose of the CTBT. Hence the strong counter-attack by Senator Rubio and his colleagues who contend that President Obama cannot overturn President Bush’s determination and the Senate vote in 1999.

Matters of great importance are at stake here for Constitutional law, international law, and public policy. When Senators contend that a central tenet of treaty law and international law has no standing for the United States of America, one of the foundations of international security is eroded. If this view gains traction, U.S. leadership in the world will be greatly diminished, and alliance ties will be sorely tested. If the United States is not bound to respect signed agreements until the Senate provides its consent, then no one else is obliged to respect signed agreements awaiting entry into force. The United States would have no standing to complain about verification and compliance concerns for treaties that have not been ratified or entered into force. Constraints on nuclear testing could go by the boards – but not domestic constraints against the resumption of testing.

These issues warrant serious attention. They have just now seen the light of day because President Obama chose to pursue a UN Security Council resolution and P-5 statement reaffirming the CTBT.


  1. oliver (History)

    Mr. Krepon

    Leadership of the USofA in the world will be definitely greatly diminshed once TRUMP becomes president.
    What’s there for that pesky little treaty to matter much, then?

    • Michael Krepon (History)

      I’m actually hoping he is asked about the CTBT in the presidential debates.

  2. Toby Fenwick (History)

    Dr Krepon,

    As you rightly say, customary international law (in this case VCLT) is binding on the US, whether some (wilfully?) ignorant US Senators like it or not. This is not a new problem (the Avena cases are a prime example https://en.m.wikipedia.org/wiki/Avena_case) but one which makes the US either an international laughing stock or a pariah.

    Worse, since international law is based on reciprocity, each time the US refuses to honour its international obligations, US interests and nationals abroad are put at risk. I wish these GOP Senators would be slightly more responsible.

  3. Major Variola (History)

    I thought Kim figured out the Pu tricks. But now I think he simply got some centrifuges and did the “works first time” U gun plan to achieve 20kt. Good luck miniaturizing, but as some have said, Nature wants you to have nukes. And crypto.

    • J_kies (History)

      Sir; as is publically known, the Hiroshima device (little boy) was an enriched Uranium gun device with an estimated yield near 13 kT. The Nagasaki device (fat man) was a Plutonium implosion device like the Trinity gadget and held a yield near 20kT.

      The DPRK released a video including photos of Kim Jong Un inspecting what they stated to be their design of a warhead. The ‘disco ball’ was intended to look like the external case of some version of a complex implosion device. The DPRK photos had no similarity to a gun device.

      So based on history; early implosion devices have a bit more yield than early gun devices and the DPRK has consistently shown aspirations to implosion devices.

  4. Michael Krepon (History)

    key passage of P-5 statement that will accompany the UNSC resolution on the CTBT:

    We take this opportunity to reaffirm our own moratoria on nuclear weapons test explosions or any other nuclear explosions pending the CTBT’s entry into force, as such moratoria are an example of responsible international behavior that contributes to international peace and stability, while stressing that such moratoria do not have the same permanent legally binding effect as entry into force. We call on other states to do likewise, recognizing that a nuclear-weapon test explosion or any other nuclear explosion would defeat the object and purpose of the CTBT.

    entire statement can be found here: