Pressure is mounting to change the devolution settlement so that Scotland has the power to ban Trident nuclear weapons from its soil.

Trade unionists, religious leaders and anti-nuclear campaigners have called on the Calman Commission, set up by the Scottish parliament to review devolution, to investigate ways of bringing weapons of mass destruction under Scottish control.

They have been backed by one of the country's most senior legal figures, Lord Murray, who argues that the use of such weapons is illegal. Possessing them is "probably" also against international law, says the former Lord Advocate.

"This should be incorporated into Scotland's constitutional arrangements," he told the Sunday Herald. "It should be reflected by the Calman Commission."

Up to 200 thermonuclear warheads are stored behind barbed wire at the Royal Navy armaments depot at Coulport, on Loch Long. As many as 48 at a time are taken to sea from Faslane eight miles away on Gare Loch by one of four Trident submarines.

The Commission on Scottish Devolution, chaired by Glasgow University's chancellor, Sir Kenneth Calman, was established in December 2007 with the backing of Labour, the Liberal Democrats and the Conservatives. It comprises 15 members from political parties, trade unions, business and other sectors.

Among those who have made submissions to the commission on nuclear weapons is the trade union, Unison. It represents 150,000 public service workers in Scotland.

"Ideally Unison would like control over weapons of mass destruction to be devolved, but we do recognise that it will be difficult to separate this from the overall control of defence," said the union's Scottish organiser, Dave Watson.

"It is clear from the majority votes of both Scottish MPs and MSPs against the replacement of Trident that this is the view of the Scottish people and their representatives, and we think that the devolution of control over weapons of mass destruction would allow this view to be enacted."

In its submission, the Church of Scotland pointed out that Scottish public opinion on nuclear weapons was "significantly different" from that of the UK as a whole. While it may not be possible for Holyrood to take ultimate control of the weapons, the church argued, "the commission may wish to consider how better the structure can reflect distinctive views in different parts of the UK".

According to John Ainslie, the co-ordinator of the Scottish Campaign for Nuclear Disarmament, there was a specific clause in the Scotland Act reserving control over weapons of mass destruction to Westminster.

"A small change to one line may be all that is needed to give the Scottish parliament the power to prohibit their deployment in Scotland," he said.

"A clear majority of Scots want Holyrood to have the power to remove Trident from the Clyde. Sir Kenneth Calman and his team should use their considerable talents to work out how to adjust the devolution settlement so that this popular demand can be satisfied."

Scottish CND's submission to the Calman Commission has been supported by the Roman Catholic Archbishop of St Andrews and Edinburgh, Cardinal Keith O'Brien.

"I hope that the contents of the submission from Scottish CND receive considerable publicity," he said. The Edinburgh Peace and Justice Centre, based at St John's Church, Princes Street, argued that Trident was immoral and criminal. "We believe the people of Scotland would be better served if the control of weapons of mass destruction were now devolved to the Scottish parliament," the centre said.

The Calman Commission aims to publish its first report before the end of 2008, and a final report in 2009. "The commission has received a large number of submissions covering a range of issues, all of which are given fair consideration," said a commission spokesman.

"The commission's process of gathering evidence remains ongoing and it would be premature to say it has reached a definitive view on the issue at this relatively early stage of its work."