The adoption of the landmark Treaty on the Prohibition of Nuclear Weapons by a vote of 122 to 1 at the United Nations in New York on 7 July provides a historic watershed; a moment of truth regarding the only weapons which pose an existential threat to humanity and our living planet.

It's no coincidence that all the states armed with nuclear weapons, and those complicit in their possible use, oppose the treaty. These states have come up with a whole raft of changing claims as to why the treaty will not only be ineffective, but dangerous. Publicly they claim that the treaty ignores security concerns, will be ineffective because it doesn't involve nuclear-armed states, that nuclear weapons should only be prohibited after they have been eliminated, that the treaty will exacerbate divisions between states with and without nuclear weapons, even that it will threaten strategic stability and increase the danger of nuclear war (a claim made by the Russian ambassador to the U.N. in New York).

Privately they tell a different story. In October 2016, before the U.N. vote on ban treaty negotiations, the U.S. admonished its NATO allies to vote "no," and if negotiations started, to stay away. They recognized that a ban treaty "aims primarily to stigmatize nuclear weapons and...delegitimize the concept of nuclear deterrence," that it "could impact non-parties as well as parties, and could even have an impact prior to its entry into force," and interfere with NATO preparations to use nuclear weapons. That is, the treaty would work as intended.

The response from France, the U.K. and the U.S. when the treaty was adopted was immediate and angry: "We do not intend to sign, ratify or ever become party to it...Accession to the ban treaty is incompatible with the policy of nuclear deterrence." Essentially they are saying that they are determined to continue to threaten to use nuclear weapons, and that they do not intend ever to fulfill their vow to disarm. The opposition the treaty has aroused from nuclear-armed and -dependent states is powerful evidence that it matters. They clearly cannot ignore the treaty, and it has put them on the defensive.

The claim that the ban treaty undermines the Nuclear Non-Proliferation Treaty could hardly be further from the truth. Governments negotiating the treaty went to great lengths to reinforce the NPT. Article 6 of the NPT obliges all governments to "pursue negotiations in good faith on effective measures...relating to nuclear disarmament." Comprehensively prohibiting nuclear weapons as the ban treaty does is clearly "an effective measure." Its provisions for the verified, irreversible elimination of nuclear weapons and nuclear weapons programs and facilities complement and build on the NPT and apply consistent standards to all states, essential to delivering disarmament and breaking the current "nuclear apartheid" logjam.

Another mischievous claim is that the ban treaty weakens the nuclear safeguards provided for by the NPT. In fact, it does nothing of the sort. It clearly stipulates that states joining the ban treaty must maintain their safeguards obligations; if they do not yet have a safeguards agreement they must bring one into force. In both cases the treaty anticipates that states may adopt additional safeguards in the future.

The ban treaty provides pathways for states that have repudiated nuclear weapons, have nuclear weapons currently, have had them in the past, have nuclear weapons stationed on their territory, or assist in military preparations for their use. No state can legitimately claim that this treaty is not for them. If they are committed to disarmament they will sign; if they do not join, whatever they say, they are part of the problem and not the solution.

(Tilman Ruff is co-president of International Physicians for the Prevention of Nuclear War and founding international and Australian chair of the International Campaign to Abolish Nuclear Weapons -- ICAN -- which was awarded the Nobel Peace Prize for 2017.)