There is a short litmus test to know if UN Security Council sanctions against Iran have snapped back.Is the 2015 Iran deal finally dead? If it’s not, and none of the remaining five signatories to the deal have claimed that it is, then UNSC sanctions against Tehran have not been restored, irrespective of what the US says. Then why is US Secretary of State Mike Pompeo going around talking about the sanctions snapback?Because it is the last ray of hope the US has, short of its own economic power, to ensure that the UNSC arms embargo against Iran is not lifted on October 18th.It’s a particularly scary scenario for both the US and Israel, particularly given that the Trump Administration believes that Iran could have enough fissile material to produce a nuclear bomb by the end of the year.In an attempt to prevent the strengthening of Iran’s conventional and non-conventional arms arsenal, Pompeo in August triggered a 30-day mechanism in the Iran deal, known as the Joint Comprehensive Plan of Action (JCPOA), that allows for the snapback of international sanctions.Those sanctions, including an arms embargo, were lifted in 2015 in exchange for Iran’s agreement to sign a deal with six world powers to curb its nuclear weapons program.Any of the six powers that signed the deal with Tehran can snap back the sanctions for non-compliance. The US was one of the signatories, but it left the deal in 2018, a move which has cast legal doubt on its ability to trigger the snapback sanctions.US President Donald Trump lives in a “parallel universe,” Iranian Foreign Minister Javad Zarif charged on twitter after hearing Pompeo state that the sanctions had been reimposed.“The world says NO Security Council sanctions were restored,” Zarif wrote, adding “@realDonaldTrump should change tack before @SecPompeo further turns #MAGA into a global laughing stock.”It was the kind of dismissive statement that one might expect from Iran in any scenario.But his word carried more weight, due to the vast gulf, between US statements about the sanctions and the reality on the ground at the UN.Thirteen of the 15 UN Security Council members have rejected the Trump administration’s argument and have insisted that Iran still enjoys sanctions relief.Even UN Secretary-General Antonio Guterres has turned his back on the US, insisting that he can only take action on the matter under direction from the UNSC.In short, he has turned the matter over to the UNSC to sort it out, and the UNSC has no interest in siding with the US.The dramatic diplomatic showdown has taken place on the sidelines of the opening of the UN General Assembly in New York, which has marked its 75th year with a focus on multilateralism. A resolution on the matter and the importance of the UN was unanimously approved by the General Assembly.The US, which hosts UN headquarters in New York and has been its largest funder, spoke of the body’s importance at the GA on Monday.“The UN was founded to promote peace and save succeeding generations from the scourge of war, and reaffirm faith in fundamental human rights. In many ways, the UN has proven to be a successful experiment,” Deputy US Ambassador Cherith Norman Chalet told the General Assembly.But in spite of her words the Trump administration has been largely dismissive of traditional multilateral bodies and has been particularly dismissive of the UN.Even in her celebratory remarks, Chalet noted, that the UN was “too often lacking in transparency, and too vulnerable to the agenda of autocratic regimes and dictatorships.”Under Trump the US has not hesitated to stand alone, at the UN, at times it almost appeared to relish the image of the lone country fighting for what was right and great in the world. Nowhere has that been more true, when it comes to Iran.On Monday, with no positive word from the UNSC the US flexed its muscles as a world power and imposed its own sanctions against those involved in Iran’s nuclear and weapons program.It was its latest attempt to pressure the international community to take a stand against Iranian aggression.There is something iconically American about the vision of the US as a lone warrior against Iran’s Islamic regime, that harks back to the vision of the US cowboy alone on the Western prairie.True it is not entirely alone. It has the support of Israel and a number of Arab states. But their numbers are far short of what is required.The call for the snapback might help the US legally as it moves forward. In an ironic show of why multilateralism matters, however, there may be little the US can do as a lone actor at the UN to ensure that an arms embargo against Iran remains in place.