There has been much talk about a fatwa - a juristic ruling issued by Iran's Supreme Leader outlawing the use of nuclear weapons. But how binding is this ruling and has it actually been made?
There has been considerable discussion of late about a fatwa reportedly issued by the Supreme Leader of Iran, Ayatollah Ali Khamenei, outlawing the use of nuclear weapons.
The existence of this 'fatwa' is regarded by its proponents as a sound basis upon which the current impasse on Iran's controversial nuclear programme can be satisfactorily resolved. 
The fatwa is considered to be a religious ruling by Iran's highest religious authority which is binding upon the Iranian state, to include the government along with the military and other associated agencies. The attraction of such a fatwa is clear in the absence of trust that persists and the urgent need for confidence building measures, but there are important questions that need to be addressed before constructive progress can be made.
The Nature and Status of a Fatwa
A fatwa may be best described as a judicial ruling based on scriptural interpretation. In order to qualify to issue a fatwa, a cleric must have attained the rank of 'Ayatollah' and be recognised as a mujtahid, one than can practise ijtehad, which roughly translates as exegesis. This sort of binding exegesis is a peculiarity of Shia epistemology and does not apply to Sunni Islam.
Fatwas are traditionally considered binding upon the followers of a particular Mujtahid and it was not uncommon for different Ayatollahs to provide different readings and interpretations of particular questions. The more senior an Ayatollah is considered, the more binding and universal the remit of the fatwa. Traditionally, the fatwa of a living mujtahid supersedes that of a deceased mujtahid, although this obviously requires a living mujtahid to issue a new fatwa.
A fatwa is traditionally written in response to a question and is couched within the scholarly apparatus of Shia exegesis; that is, depending on the nature and importance of the question, and the qualifications of the mujtahid in question, the fatwa should refer to the scriptural evidence it draws on to justify the ruling. With the advent of the internet and the ability of devotees to ask questions online, on a variety of issues, answers have tended to become shorter, stressing the ruling rather than the reasoned argument that led to it. Nonetheless, even on the internet, the question is stated and followed by an answer. Brevity is also facilitated by the relative authority of the ruling mujtahid. A senior cleric may get away with the brief answer to a question on the basis that his authority would not be challenged. Ideally however the fatwa should exist in written form and applies to self-conscious disciples of the Ayatollah in question.
Ayatollah Khamenei's Theological Status
Supporters of the existence of the fatwa argue that Khamenei's status as Supreme Leader make the fatwa binding upon the State. They also argue that given his status he only has to pronounce his views for it to be regarded as a judicial ruling (fatwa). Consequently, a series of statements and speeches in which he alludes to the nuclear question is regarded by supporters as a fatwa. It is however, highly unusual for a fatwa, however brief, not to be written down in some form. Moreover the validity of an 'oral' fatwa relates in part to its form of transmission (in a pre-literate and mass communication society, one might only be expected to hear a fatwa); and to the relative importance of the question being asked.
To suggest that we have a fatwa relating to a matter of national security, existing purely in oral form, and that at no time since the initial pronouncement in 2003 was it thought useful to write such an important juridical opinion down, undermines its significance. It also effectively implies that in Iran, Khamenei governs by decree, and that his pronouncements should simply be read as sacred injunctions.
The notion that he would simply utter a statement which would then be read as a fatwa is not only controversial in its own right; such a position would likely be challenged by other Ayatollahs who are critical of Khamenei's theological credentials, let alone possessing the authority to issue unsubstantiated opinions of this nature. It does not help matters that other senior Ayatollahs have actually issued written fatwas condemning the possession and use of nuclear weapons. Curiously, Khamenei has never defined his comments as a fatwa and they do not appear as such on his website.
Khamenei could go some way to answering these criticisms by issuing a detailed written exegesis substantiating his opinion, firmly anchored in scripture such that it would not be easily overturned by another fatwa, either by himself or another Ayatollah. At present, the existence of an 'oral' fatwa with no written support tells us more about the state of modern Iranian politics, and Khamenei's perceived position within it, than any meaningful basis for the resolution of a crisis.
The notion that a fatwa is sacred and binding - quite apart from the difficulties this would normally incur for the notion of continuous interpretation that is central to Shia epistemology - is further complicated by the precedence provided by the Islamic Republic itself. We have, crucially, the example of the fatwa against Salman Rushdie issued by the founding father of the Islamic Revolution, Ayatollah (Imam) Khomeini. This fatwa was also much debated at the time since it was not clear what question had been asked and whether the standard procedure had in fact been followed.
Given the status of Ayatollah Khomeini, these points were largely dismissed. Furthermore, when the details of the fatwa were 'explained' by the then president, one Ali Khamenei (then at a lower clerical rank of Hojjat-ol Islam, not an Ayatollah) to the effect that if Rushdie apologised the fatwa could be removed, he was swiftly rebuked by Khomeini who categorically stated that this was not the case and the judgment of death had to be carried out.
So far so good as far as the inviolability of a fatwa is concerned. However the problem arose after Khomeini's death when Iranian diplomats and politicians spent the better of part of a decade trying to argue that the fatwa was only religiously binding and not politically relevant to the state; that it was not a fatwa at all but a decree (hokm) and that religion and politics had always been separate in Iran (an awkward position to take given the thrust of the Islamic Revolution). The point is that the crisis was resolved in 1998 when the Iranian government agreed not to pursue it. This flatly contradicts the position currently being argued with regard to the nuclear fatwa.
There can be little doubt that the existence of a 'nuclear fatwa' would be a useful basis on which to build a satisfactory resolution to the current crisis. But there also can be little doubt that at present such a fatwa - in any meaningful form - does not appear to exist. The concept of an 'oral fatwa' in the context of Iran's nuclear programme, is meaningless and for any such ruling to have any weight it should be detailed and substantiated, and ideally supported by a broad range of the senior clerical hierarchy in Iran today.
This surely cannot be beyond the capabilities of the vast bureaucracy that is the Supreme Leader's office? A fatwa of this nature would make a substantive and interesting document that could and should be taken seriously. It would also convey to the outside world the seriousness with which Iran takes the issue, and be a sound basis for possible progress, and something tangible to operationalise.
 Juan Cole, for example, takes the view that Khamenei's pronouncement does indeed equate with a fatwa. Details of the putative fatwa can be found here.
 For a more detailed discussion see: Michael Eisenstadt and Mehdi Khalaji, 'Nuclear Fatwa, Religion and Politics in Iran's Proliferation Strategy', Washington Institute for Near East Policy, Policy Brief No. 115, September 2011.
 See for example Ayatollah Montazeri's response to Mohsen Kadivar's questions: http://kadivar.com/?p=128 and http://kadivar.com/?p=168
Senior Associate Fellow; Professor of Iranian History and Director of the Institute for Iranian Studies, University of St Andrews