The prime minister’s advisory panel on national security has recommended a reconsideration of Japan’s adherence to the so-called three nonnuclear principles. The panel specifically urged that the third principle, the prohibition on the introduction of nuclear weapons into Japan (which forbids not only the stationing of weapons in Japan, but even the transit of weapons through Japan), be relaxed in order to permit the U.S. greater freedom in deploying nuclear weapons in Japanese territory.
This is a bad idea for many reasons, but for one it would be inconsistent with the Constitution.
As is well known, Article 9, paragraph 1 of the Constitution renounces war and the threat or use of force as sovereign rights of the nation, while paragraph two prohibits the maintenance of armed forces or other war potential, and denies to Japan the right of belligerency. The long established official understanding of paragraph 1 is that Japan can only use the minimum military force necessary for its individual self-defense. It cannot use or threaten the use of armed force for collective self-defense, or for U.N. collective security operations.
Even this understanding, long embraced by successive governments, the courts, and the Cabinet Legislation Bureau, is a strained interpretation of a clause that clearly prohibits those uses of force that remain sovereign rights under international law — which are limited to individual and collective self-defense, and collective security operations. But the proposed changes to the nonnuclear principles would violate Article 9 under even the official interpretation.
The three nonnuclear principles were articulated by the government of Prime Minister Sato in 1967, and formally adopted in a Diet Resolution. Japan went on to sign the Nuclear Nonproliferation Treaty in 1970 and ratified it in 1976. The nonnuclear principles caught the imagination of the Japanese people and quickly became powerful elements of the broader pacifist identity associated with the constitution. As the only victim of nuclear weapons, this stance also made Japan a powerful symbol for the nonproliferation movement. Sato won the Nobel Peace Prize for his efforts.
Of course, reality is always more complicated and messy. Sato had in fact sanctioned a study to determine whether Japan should develop a nuclear weapons program. Only after deciding against it did he articulate the nonnuclear principles. Moreover, in 1969 he then entered into a secret agreement with U.S. President Richard Nixon and U.S. Secretary of State Kissinger to permit the stationing of nuclear weapons in Okinawa (then still under American control) in the event of a crisis.
Recently discovered evidence confirms that a secret agreement has also existed from even earlier, permitting American forces to “introduce” nuclear weapons into Japan itself without prior consultation, in clear violation of the third nonnuclear principle. The advisory panel actually argues that since the practice has been going on secretly, it should simply be formalized, and the principle prohibiting it abandoned.
That is absurd. When someone betrays an agreement or violates a compact, the response is not to formalize and perpetuate the breach, but to take measures to ensure that the violation cannot continue.
Which brings us back to the Constitution. Leaving aside the suspicion that the panel is also obliquely suggesting that Japan should consider developing its own nuclear weapons (a suggestion that has been advanced by politicians several times recently), even the presence of U.S. nuclear weapons in Japan would likely constitute a violation of Article 9.
First, such nuclear weapons could not be construed as being for the individual self-defense of Japan. While they would no doubt be part of the nuclear umbrella that serves to protect Japan, in legal terms the use of the weapons, and even their deterrent power (which effectively constitutes the threat to use the weapons), would not be for the exclusive defense of Japan, but rather would be for the defense of the United States, its other allies and perhaps its “vital interests.”
This is in fact consistent with recent U.S. National Security Strategy. It should also be noted in passing that while the deployment might be strategically useful for the U.S., it is certainly not necessary.
Moreover, it is very dubious whether the use of nuclear weapons could ever constitute self-defense as the concept is understood in international law. The Cabinet Legislation Bureau opined in 1959 that nuclear weapons could possibly be “defensive” in nature. Since then, however, the International Court of Justice, in its 1996 Advisory Opinion on the Legality of the Threat or Use of Nuclear Weapons, held that it is improbable that the use of nuclear weapons could ever meet the tests of necessity and proportionality so as to be justified as self-defense.
The International Court of Justice also suggested that it was unlikely that such use could ever satisfy the humanitarian law prohibition against the indiscriminate and disproportionate killing of civilians. The threat of such use would similarly run afoul of the prohibition against the threat to use force, found in both the U.N. Charter and Article 9.
Some will argue that the weapons would not be under the command and control of the Japanese government, so would neither constitute the prohibited “war potential,” nor be the basis of a “threat or use of force” attributable to Japan. The Supreme Court of Japan famously decided in the 1959 Sunakawa case, using just such logic, that the U.S. armed forces in Japan did not constitute the “maintenance of war potential” as prohibited by paragraph two of Article 9.
But that was 50 years ago. The definition of aggression adopted by the U.N. General Assembly, and subsequently applied by the International Court of Justice, attributes culpability for aggression to states that permit their territory to be used by other states or entities for acts of aggression or the launching of armed attacks. Indeed, that principle was the justification for the U.S. invasion of Afghanistan following 9/11.
The same principles of attribution would apply by analogy to any use of weapons launched from Japanese territory, even if they did not constitute an act of aggression. These principles should therefore help shape the constitutional analysis as well. Thus, Japan cannot sidestep the constitutional prohibitions against maintaining “war potential” and the “threat or use of force,” through coy arguments that the nuclear weapons being deployed in Japan, with Japanese knowledge and consent, are not under Japanese command and control.
The “revision” of the nonnuclear principles would therefore require amending the Constitution to permit the use of force for collective self-defense, and the maintenance of “war potential” consisting of nuclear weapons.
There are many reasons why doing so would be ill-advised. But choosing to simply ignore the constitutional issues, and proceeding with changes to the nonnuclear principles that would lead to violations of the Constitution, would have much more serious consequences, both inside and outside of Japan.
Changing the nonnuclear principles would undermine the normative power of the constitutional system, raise questions about the country’s commitment to the rule of law, and reawaken the deepest suspicions among its neighbors.