Iranian President Mahmoud Ahmadinejad's impending visit to the United States and the UN is a cruel parody of law and justice that will put us on the wrong side of history.Ahmadinejad will enter the US despite being inadmissible under American law. He will address the United Nations General Assembly despite being in violation of its UN Charter and international law. And, he will be indulged – even feted – by universities, institutes, and the media, thereby sanitizing his crimes and mocking the suffering of the Iranian people.This charade – repeated annually since 2007 – ignores and undermines basic principles of domestic, international, and humanitarian law.First, President Ahmadinejad belongs on the US “Watchlist" of persons barred from entry – those who “aid terrorists … persecute religious minorities … or commit or incite to genocide” are prohibited from entering the United States. Indeed, President Obama issued a proclamation just last month barring entry for persons “who participate in serious human rights and humanitarian law violations and other abuses.”Indeed, the evidence of Iran's and Ahmadinejad’s criminality on each of these counts is clear and compelling. In the matter of international terrorism, the recent US State Department Annual Report lists Iran as a leading state sponsor of international terrorism. Ahmadinejad’s Iran recruits, trains, finances, instigates and arms its terrorist proxies such as Hamas and Hizbullah, whose platforms and policies are replete with genocidal calls.Under Ahmadinejad, Iran has intensified its persecution and prosecution of religious minorities, especially the Baha’i – its largest religious minority – whose members are subject to harassment, repression, torture, imprisonment, and execution. As for Christians, whose persecution has also accelerated, even praying together is a criminal act.Ahmadinejad’s violations of the Genocide Convention’s prohibition against "direct and public incitement to genocide" – symbolized by the parading the streets of Tehran of a Shiab-3 missile draped with the emblem “Wipe Israel off the map” – is cause alone for exclusion.Ahmadinejad’s systematic and widespread assaults on the rights of his own people, evident in the pervasive and persistent assault on women, students, workers, dissidents, journalists, and academics – and those who would defend them – are tantamount to crimes against humanity against his own people.Instead of being granted a podium at the UN General Assembly, Ahmadinejad should be the object of a criminal indictment. Simply put, a person who pursues the most destructive weaponry in violation of Security Council resolutions; who has already committed the crime of incitement to genocide in violation of international law; who is complicit in crimes against humanity; who engages in massive domestic repression against his own people – the whole assaultive of the basic tenets of the UN Charter – such a person belongs in the dock of the accused, not at the world’s most watched podium.Ahmadinejad’s visit to New York this year – on the 10th anniversary of the horrific tragedy of 9/11 – is the cruelest of insults. Newly unearthed and explosive testimony implicates Iran in the planning and orchestration of the 9/11 terror attacks. For Ahmadinejad to visit just blocks away from ground zero – while continuing to facilitate base and sanctuary to Al-Qaida – is an unspeakable affront to the victims and families, the people of New York, and the international community.That Columbia University may host a “dinner and dialogue” with him is reprehensible. Would Columbia invite the leader of Al-Qaida to dinner? Perhaps yes, given on the occasion of Ahmadinejad’s last visit Dean John Coatsworth asserted they would give even Hitler a platform.Yet, Ahmadinejad has been admitted before and is likely to be admitted again. How can this be?In 1947, the US and the UN signed a treaty wherein the US agreed not to impede access of representatives of Member States to the UN Headquarters in New York. This “Headquarters Agreement” is said to trump American domestic law. But the Vienna Law of Treaties states that jus cogens – the preemptory norms of international law – such as crimes against humanity – override any treaty. Ahmadinejad’s crimes are such crimes. The Headquarters Agreement should not avail and must not prevail.Nor would this be the first time a sitting head of state was denied entry. Austria’s Kurt Waldheim was barred for complicity in war crimes. He was only a solider; Ahmadinejad is a general.If the US allows him entry, Ahmadinejad’s travel should be restricted to only those parts of New York under UN control, the Iranian Mission, and the airport. The US government is not obliged to treat him as an innocent tourist – let alone celebrity – but rather, should isolate and shun him as the war criminal he is; Columbia University should do likewise.Even if none of these options is exercised, there are ways to break this cycle of impunity. In a word, the international community, led by the US, should act in solidarity with the oppressed people of Iran, and should not serve as a shield or platform for their oppressors. Countries like the US and Canada should fulfill their responsibilities under international law – including the Genocide Convention – and refer the Iranian leaders’ criminal incitement to genocide to appropriate UN agencies. It is astonishing that this criminal incitement has yet to be addressed by any UN body, though the UN finds it fit to give Ahmadinejad a podium.Inter-state complaints against Iran could be initiated at the International Court of Justice, while Ahmadinejad and his cohorts could be made to answer for their crimes at the International Criminal Court.President Ahmadinejad and other Iranian leaders should be placed on a "watchlist" by concerned countries, preventing their entrance as "inadmissible persons."Finally, comprehensive, consequential, and targeted multilateral sanctions should be adopted – and enforced – not only for Iran’s continued pursuit of nuclear weapons, but also for its sponsorship of international terrorism and massive violations of human rights.History shows that sustained international juridical efforts can bring dictators like Milosevic and Pinochet to justice. Our choice is clear: We can either act or be on the wrong side of history.Irwin Cotler is a Canadian Member of Parliament and is the former Minister of Justice and Attorney General of Canada. He is a Professor of Law (Emeritus) at McGill University and has written extensively on Iran and has previously prosecuted for incitement to genocide.