When the US endorsed the use of chemical weapons
At this time when President Obama has declared the use of chemical weapons by the Syrian regime to be a US “red line”, with dire (though unspecified) consequences for the regime, it is appropriate to recall a time when the US endorsed the use of chemical weapons and took the lead in blocking Security Council condemnation of their use.
Here, we are not talking about a few instances of use in small amounts (which the US and others allege has already happened in Syria) but systematic use as an integral part of military operations carried out over several years against both military and civilian targets.
We are, of course, talking about Iraq’s use of chemical weapons in its aggression against Iran from 1980-88 and US support for Iraq in that aggression in order to prevent an Iranian victory.
To remind readers of the extent of this support, I reproduce in the Annex below an extract from Richard Clarke’s book Against All Enemies. He worked in the US State Department at the time and played a part in drawing up US options “to prevent an Iraqi defeat” (and later worked in President Clinton’s White House as his anti-terrorism chief).
Supreme Leader forbad use of chemical weapons
Iraq’s use of chemical weapons against Iran in the 1980s is worth recalling for another reason as well – for the fact that Iran didn’t retaliate in kind, even though it had the capacity to do and the Iranian military leadership wanted to do so. It didn’t do so because the Supreme Leader, Ayatollah Khomeini, forbad the use of chemical weapons as a violation of Islamic law.
As Flynt Leverett explained recently:
“In its war with Iraq – when the United States, among others, was supporting Saddam Husayn in an eight-year war of aggression against the new Islamic Republic – Ayatollah Khomeini’s own military leaders came to him and said, ‘We inherited the ability to produce chemical weapons agent from the Shah. We need to do that and weaponize it so that we can respond in kind. We have tens of thousands of our people, soldiers and civilians, who are being killed in Iraqi chemical weapons attacks. We need to be able to respond in kind.’ And Imam Khomeini said, ‘No, because this would violate Islamic morality, because it is haram – it is forbidden by God – to do this, and the Islamic Republic of Iran will not do this.’” 
So, not only did Ayatollah Khomeini declare that the use of weapons of mass destruction was in violation of Islamic law, he insisted that the Islamic Republic acted upon that principle and eschewed the use of chemical weapons, even though it was engaged in a life or death struggle with Iraq, which had the support of the US and most of the Arab world.
Nuclear weapons a “grave sin”, says Supreme Leader
Today, Iran’s leaders, including President Ahmadinejad, have repeatedly denied that they have any ambitions to develop nuclear weapons. Ayatollah Khomeini’s successor as Supreme Leader, Ayatollah Khamenei, has followed him in declaring that the acquisition or use of nuclear weapons would also violate Islamic law, describing the possession of such weapons to be a “grave sin”.
For example, in a speech to nuclear scientists on 22 February 2012, he said:
“The Iranian nation has never pursued and will never pursue nuclear weapons. There is no doubt that the decision makers in the countries opposing us know well that Iran is not after nuclear weapons because the Islamic Republic, logically, religiously and theoretically, considers the possession of nuclear weapons a grave sin and believes the proliferation of such weapons is senseless, destructive and dangerous.” 
There was nothing new in this statement from him. In 2005, he issued a fatwa – a religious edict – saying that “the production, stockpiling, and use of nuclear weapons are forbidden under Islam and that the Islamic Republic of Iran shall never acquire these weapons” (see Iran’s Statement at IAEA Emergency Meeting, 10 August 2005 , p121). And he has repeated this message many times since then (see, for example, Juan Cole, ‘Khamenei Takes Control, Forbids Nuclear Bomb’, 4 March 2012 ).
These repeated pronouncements by Khamenei should be taken as a serious indicator of Iranian policy on this matter, not least because similar pronouncements by his predecessor resulted in the Islamic Republic shunning the use of chemical weapons to repel Iraqi aggression.
Also, Khamenei is the person who would take any decision that Iran develop nuclear weapons. If he intends to do so in the near future, it is surely unwise of him to declare repeatedly that these weapons are un-Islamic – yet he continues to do so.
Of course, it is not impossible for Khamenei or a future Supreme Leader to reverse this stance. However, as Flynt and Hillary Mann Leverett point out in their book Going to Tehran: Why the US must come to terms with the Islamic Republic of Iran, this “would mean having to explain – to Iranians and to the entire Shi’a world – how Iran’s strategic circumstances have changed to such an extent that manufacturing nuclear arms was now both necessary and legitimate” (p87). They continue:
“That, of course, is not an absolute constraint on Iranian weaponisation. But it would require, at a minimum, a widely perceived and substantial deterioration in the Islamic Republic’s strategic environment – most plausibly effected by an Israeli and/or US attack on Iran. It is far from certain that Tehran would opt for weapons acquisition then. But those urging military action to block the Islamic Republic’s nuclear advancement advocate a course that would raise the risk of Iranian weaponisation, not reduce it.”
In other words, Israeli or US military action against Iran, ostensibly to prevent Iran developing nuclear weapons, would be likely to have the opposite effect, leading the Iranian leadership to conclude that the possession of such weapons was the only means of deterring future attacks.
Withdraw from NPT in 1979
A final point: if the Islamic Republic had intended to develop nuclear weapons, it should surely have withdrawn from the Nuclear Non-Proliferation Treaty (NPT) after the Islamic Revolution in 1979 and become free, like Israel, from international obligations not to develop nuclear weapons. Then, it reviewed all the international agreements and treaties concluded under the Shah, including the NPT, but it decided to maintain its membership of the NPT and adhere to its existing nuclear safeguards agreement with the IAEA.
Because of Israel’s growing nuclear arsenal, withdrawal from the NPT in 1979, or any time since, would have been within Iran’s rights under the NPT, Article X of which says:
“Each Party shall in exercising its national sovereignty have the right to withdraw from the Treaty if it decides that extraordinary events, related to the subject matter of this Treaty, have jeopardized the supreme interests of its country. It shall give notice of such withdrawal to all other Parties to the Treaty and to the United Nations Security Council three months in advance. Such notice shall include a statement of the extraordinary events it regards as having jeopardized its supreme interests.” 
By any objective standard, Iran and other neighbours of Israel have good grounds for withdrawal, because of the build up over the past 40 years of an Israeli nuclear arsenal directed at them. There could hardly be a better example of “extraordinary events, related to the subject matter of this Treaty”, which “have jeopardized [their] supreme interests”.
It might not have been wise for Iran to withdraw from the NPT at any time in the past 40 years, since it would risk terrible havoc from theUS and/or Israel. But, there is no doubt that such an action would be fully justified under the provisions of the NPT.
Annex: US options for preventing Iraqi defeat
Extract from Against All Enemies by Richard Clarke (p41-2)
“Shortly after it began, the Iran-Iraq war became a stalemate, with very high casualties on both sides. Our little politico-military team at State was asked to draft options to prevent an Iranian victory or, as we entitled one paper, ‘Options for preventing Iraqi defeat’. At time passed and the war continued, many of those options were employed. Although not an ally of Iraq, the Reagan administration had decided that Saddam Hussein should not be allowed to be defeated by a radical Islamist, anti-American regime in Tehran.
“In 1982, the Reagan administration removed Iraq from the list of nations that sponsored terrorism. Iraq was thus able to apply for certain US government-backed export promotion loans. Then in 1983 a presidential envoy was sent to Baghdad as a sign of support for Saddam Hussein. A man who had been the Defense Secretary seven years earlier in a previous Republican administration was sent carrying a Presidential letter. The man was Donald Rumsfeld. He went to Baghdad not to overthrow Saddam Hussein, but to save him from probable defeat by the Iranian onslaught. Shortly after, I saw American intelligence data flow to Baghdad. When Iran was preparing an offensive in a sector, the Iraqis would know what US satellites saw and Saddam would counter with beefed up defenses.
“In 1984, the United States resumed full diplomatic relations with Iraq. Although the US never sold arms to Iraq, the Saudis and Egyptians did, including US arms. Some of the bombs that Saudis had bought as part of overstocking now went to Saddam, in violation of US law. I doubt that the Saudis ever asked Washington’s permission, but I also doubt that anyone in the Reagan administration wanted to be asked.
“After the intelligence flow to Saddam was opened up, our State Department team was then asked to implement the next option in the plan to prevent Iraqi military defeat, identifying the foreign sources of Iranian military supplies and pressuring countries to halt the flow. We dubbed the diplomatic-intelligence effort Operation Staunch. I spent long days tracing arms shipment to Iran and firing off instructions to American embassies around the world to threaten governments with sanctions if they did not crack down on the gray market arms shipments to Tehran. The effort was surprisingly successful, raising the price and reducing the supply of what arms Iran could get.”
Lest there be any doubt that the US was aware of Iraq’s use of chemical weapons, here’s what Flynt and Hillary Mann Leverett write about the matter in their book Going to Tehran (p50)
“… for four years, the United States took the lead in blocking any meaningful action by the Security Council to stop Iraq’s use of chemical against Iranian military and civilian targets. Washington was fully aware of what Iraq was doing: during one of Rumsfeld’s visits to Baghdad, Saddam’s foreign minister, Tariq Aziz, gave the American visitor video tapes showing tens of thousands of Iranian soldiers killed by Iraqi chemical weapons, to underscore what ‘civilized Iraqis have to do in order to stop the barbarian Iranians’. But, former secretary of state George Schultz subsequently (and rather cold-bloodedly) explained, ‘It was a very hard balance. They’re using chemical weapons. So you want them to stop using chemical weapons. At the same time, you don’t want Iran to win the war.’”