The United Nations Security Council (UNSC). has ultimate responsibility for international security, war and peace. The Security Council has five permanent members - China, France, the Russian Federation, the US and the UK - and ten non-permanent members who are elected according to regional groups. The Security Council has authority under the Chapter VII of the UN Charter to "take such action by air, sea, or land forces as may be necessary to maintain or restore international peace and security".  It is increasingly involving itself in internal conflicts under the principle that they can be a threat to international peace.

In the UK ministers - in particular the Prime Minister - may determine decisions over war and peace without formal reference to Parliament, under the Royal Prerogative - a set of non-statutory powers which were once exercised by kings and queens. We  also discuss the role of the Royal Prerogative on the Improving Democratic Oversight page.

Click here also to view a description of the Royal Prerogative as supplied to the  government by the Public Administration Select Committee in 2003 and the report consequently produced by the Committee.

Such is the concentration of power in a Prime Minister's hands that he or she need not even inform or consult fully with cabinet colleagues before engaging UK forces in armed combat. In his 2004 report on intelligence and weapons of mass destruction, Lord Butler found that important discussions of the decision to participate in the invasion of Iraq took place in a small informal group of the premier's allies, by-passing the cabinet which in theory was jointly responsible.

The most relevant government departments are: The Foreign Office; the Ministry of Defence; the Department for International Development; and the Prime Minister's Office.

Under the United Nations Charter the use of force is only permitted when authorised by a Security Council Resolution - unless, as set out in Article 51 of the Charter, it is carried out as an exercise of  "the inherent right of individual or collective self-defence if an armed attack occurs against a Member of the United Nations", that is, a country has the right to defend itself from attack. 

In recent years there has been a debate about the responsibility of states and the international community to intervene for the protection of civilian populations or minorities against war crimes, crimes against humanity and genocide.  However, this is not as yet widely recognised as part of international law. 

While the UN Charter determines when a war may be fought numerous other conventions and agreements apply to the manner in which it may be conducted - for instance the Geneva Conventions.

A state carrying out military action could be found in violation of international law by the International Court of Justice (ICJ), an organ of the United Nations.  But it is an inherently weak institution. Only states may be party to full cases before the court, thereby limiting the possibility of other parties seeking redress; secondly, there is nothing to stop a state withdrawing from a case before the court at any time; and thirdly, the ICJ has no authority to enforce compliance with its judgments. 

Following an invasion leading to "regime change", such as that which occurred in Iraq in 2003, it is unlikely that the newly-installed government would bring a case against those nations which helped bring it to power.

Individuals can be tried for war crimes by the International Criminal Court (ICC), however its jurisdiction is also limited; and the ICC has yet to agree on a definition of crimes of aggression.

At national level, since policy is made using the Royal Prerogative, there is no domestic statutory framework. A long-standing tradition exists of judicial non-intervention in the exercise of the prerogative, especially where foreign affairs are concerned. The chances of successful legal action in the courts against a government over a war or military action are slight.

We have detailed above the freedom that Royal Prerogative powers give to ministers even when it comes to making war and the failings of the doctrine of individual and collective ministerial responsibility to Parliament.

It is argued that the way in which Britain was led into war against Iraq in 2003 showed British democracy to be in fine working order, with the Prime Minister not relying on the prerogative to wage war unilaterally, but winning over the cabinet, Parliament and ultimately the country. 

But this is a formalistic and disingenuous account. The reason decision to oust Saddam Hussein was taken long before the final parliamentary vote in March 2003. Labour MPs in the majority party were confronted by a stark choice - vote for war or the fall of their government - accompanied by arm-twisting and manipulation; and given false intelligence information as were MPs of the other parties and the country at large.

Even when the inquests began, the government avoided proper parliamentary scrutiny. Instead, as the Commons Liaison Committee and the Foreign Affairs Committee complained in 2004 that the government was more willing to cooperate with non-parliamentary inquiries it had established itself than those carried out by Parliament.

Two non-parliamentary inquiries were set up under terms of reference set by the government to investigate matters associated with the Iraq war: the Hutton inquiry and the Butler review.  Neither was empowered to take a full look at the way the country was led into the war.

The parliamentary committees most likely to become involved in overseeing the conduct of warfare are three select committees, all in the Commons: the Defence Committee, the Foreign Affairs Committee and the International Development Committee.

There is also a non-parliamentary committee comprising MP and peers, appointed by the Prime Minister in consultation with opposition parties, the Intelligence and Security Committee.

Other tendencies mitigate further against effective parliamentary oversight of war. There is a convention that governments do not disclose advice provided to them by their law officers - meaning that Parliament is kept unaware of the detail of the counsel provided to the executive as to the legality of an action. If a military emergency occurs during a parliamentary recess, MPs and peers may be denied the chance even to debate it since the power to recall Parliament lies with ministers.

Britain's membership of the North Atlantic Treaty Organisation (NATO) is its single most significant defence commitment.  NATO is a military alliance formed out of the North Atlantic Treaty of 1949, a product of rising concern in the west about the Soviet Union's military and political intentions in Europe.

Following the end of the Cold War in 1991, former Eastern Bloc countries joined NATO and its membership now stands at 26. NATO has been an important part of the post-war Special Relationship between the UK and US.

Through its participation in NATO the UK cedes significant sovereignty since Article 5 of the Treaty requires those party to it to treat "an armed attack" against one or more of them in Europe or North America as "an attack again them all". This article was not triggered until the terrorist attacks on the US of 11 September 2001, though NATO had already taken military action against Bosnian Serb aircraft in 1994; and to prevent atrocities in Kosovo in 1999.

Britain has a prominent role in the ongoing NATO operation in Afghanistan which began in 1999. This engagement  - entered into under the Prerogative - did not receive formal parliamentary approval; nor were MPs invited to provide affirmative support to a substantial change in the mission parameters and increase in the UK troop deployment in 2006.

NATO is highly secretive, not only in itself but also in its influence on the release of official information in member countries. It has resisted attempts to make its security of information requirements public, despite the fact that these impose strict conditions upon the freedom of information regimes of member states. There is a NATO Parliamentary Assembly comprising parliamentarians from member states. But it does not hold the council formally to account, though the NATO Secretary-General responds to its recommendations. There is no formal mechanism for members of the Assembly to report back to Parliament.

Initial UK entry into the North Atlantic Treaty and its agreement to its subsequent expansion was carried out under the Royal Prerogative, meaning the formal consent of Parliament was not required. Nor was it sought. In 1999 the Commons Defence Committee noted that of the then 16 member states "only Canada shares with the UK a ratification process which requires no formal involvement from the legislature." The Defence Committee has carried out valuable scrutiny of NATO organisation and activity, including a detailed report on the Kosovo action.

1.  All prerogative powers should be placed on a statutory basis, making Parliament the ultimate authority on going to war and giving it a say - wherever possible in advance - over military action. Click here to see the evidence of Democratic Audit to the House of Lords Constitution Committee for its inquiry into war-making powers. This change has been advocated by others, including the Commons Public Administration Committee in a 2004 report, Taming the Prerogative.

The Constitution Committee ultimately argued that rather than placing the prerogative on a statutory basis there should be a convention established requiring government to consult Parliament preferably in advance of going to war. We believe such a convention would prove too flexible to be effective.

2.  Democratic Audit recommended to the Constitution Committee that a joint committee of both Houses should be established to take a strategic and "joined-up" view of external policies and international security across the board to complement the activities of departmentally-based select committees.

3.  We set out other changes to the way Parliament is organised in Improving Democratic Oversight above. Parliamentary committees should be enlarged and given substantially more resources; a National External Audit Office should be set up within Parliament; select committees should "mainstream" external policies;  Parliament should have its own legal counsel office to provide MPs and peers with their own legal advice; and Parliament should assume the right to recall itself in emergencies independently of the executive.

4.  Other reform proposals with relevance to armed conflict and the conduct of international policy in accordance with democratic values include the development of the principle of humanitarian intervention . See the Responsibility to Protect website; and a report by the UN Secretary General's High-level Panel on Threats, Challenges and Change.