Last weekend, I set out the position I believe the Scottish National Party will support, namely that a written Constitution of an independent Scotland should have an explicit ban on nuclear weapons – or indeed any weapons of mass destruction – being based in Scotland.

This constitutional proposal reinforces the SNP's unshakable opposition to nuclear weapons and our commitment to removing Trident from Scotland – and is the context in which we are debating Nato membership at this week's party conference.

It is obviously free for any political party or other organisation to propose measures which should be in Scotland's Constitution – and the document would be subject to widespread consultation, and ultimately ratification by the independent Parliament elected in 2016.

The key point, of course, is that without the powers of independence, Scotland can achieve none of this. Indeed, unless Scotland votes Yes in 2014, we are to be subject to a new generation of Trident nuclear weapons dumped on the Clyde – in defiance of the views of a majority of MSPs, the churches, trade unions, and undoubtedly the consensus position right across Scottish society – with an obscene price tag of up to £100 billion.

Our ability to achieve the powers needed to render the basing of nuclear weapons in Scotland illegal – and have Trident removed from Scottish waters, while maintaining Faslane as a conventional naval base – will be a compelling argument in winning a Yes vote for an independent Scotland in two years' time.

An independent Scotland will be a good citizen of the world – and a good friend to our neighbours and allies. That is why as Scotland prepares to take our place in the world, I believe it is right that Scotland continues our Nato membership as a full member state as one of 29 – subject to an agreement that we will not host nuclear weapons, in line with the vast majority of current Nato members.

As well as wanting the closest possible co-operation with the rest of the present UK, we must also recognise that Scotland's North Sea neighbours regard co-operation through Nato as extremely important. For example, air policing in northern Europe – including against potential terrorist threats – occurs through a Nato command centre in Denmark, and maritime patrol in our region is also carried out via Nato.

This is an important debate for the SNP and for Scotland – and let me say that I am proud to lead a party that is capable of discussing these matters openly, and even more importantly enabling our members and conference delegates to decide the policy after extensive debate.

To a large extent, what we are actually debating is the kind of country we want Scotland to be in the 21st century – and the values that we will hold as an independent nation and seek to translate throughout the international community by word and by deed.

As well as our opposition to nuclear weapons and support for the Non-Proliferation Treaty – a cause that Scotland will be much better able to promote inside Nato rather than outside – we also support a Scotland that respects the primacy of international law and the authority of the United Nations.

These are core values for the SNP as an internationalist party, and inform the kind of Scotland we aspire to.

For an independent Scotland remaining in Nato, we would advocate a "triple lock" governing any Scottish involvement in the deployment of international force. First, Nato must continue to respect the right of the government of each member state to decide whether to commit forces or not. Second, the deployment of any armed servicemen and women into combat situations would require to be approved by Scotland's independent Parliament. And third, above all, Scotland would only become involved in actions which carried the authority of the United Nations.

Judging by these criteria, in my view an independent Scotland could and would have participated in the UN-sanctioned, multi-nation operation in Libya last year. And without any shadow of doubt we would have stood with the overwhelming number of the international community in opposing the illegal, unilateral invasion of Iraq – which was neither Nato-led nor UN-approved.

Over the last 10 years, Scotland's conventional defence infrastructure, units and bases have been systematically dismantled by successive UK governments. While taxpayers in Scotland contribute more than £3 billion to the Ministry of Defence – far more than is actually spent here – conventional capabilities are run-down as indefensible spending on Trident nuclear weapons soars.

These are the wrong choices for Scotland – it is time to make the right choices for Scotland and our place in the world.