What exactly is the relationship between treaties and sovereignty? And is there a difference between parliamentary sovereignty and state sovereignty? I think the Leave camp is muddying the waters by talking of wanting to take back control, as if we had ever lost it.
The UK doctrine of parliamentary sovereignty comes from the Glorious Revolution of 1689. Parliament was then defined as combining Crown, Peers and Commons. Nowadays, sovereignty belongs to the elective dictatorship of the Commons. This means that the Commons could decline to act on a referendum outcome, because any referendum is advisory. However, politically, that would be difficult, in this case certainly for David Cameron but also for others. Constitutionally, the making and unmaking of treaties is still part of the royal prerogative. The monarch normally acts on the advice of the Prime Minister of the day. It was a constitutional novelty when John Major put the Maastricht Treaty to the House of Commons. But we are now in uncharted waters because of the splits within the Conservative party. Would one Tory faction decline to act on a referendum result, insist on a Commons vote, and invite other parties to support them? If they believe in parliamentary sovereignty, they should.
State sovereignty goes back to 1648 and the Treaty of Westphalia. At this point, the German states established that they were sovereign within the Holy Roman Empire. The Emperor could not interfere in their internal affairs. I have heard two different lawyer views on treaties, and I suspect they are both correct in their way. The first is that a treaty is simply an agreement between the states who signed it to do what they have agreed to do. There is no enforcement mechanism (other than war), so if one or both sides renege on their word, there will be no comeback. In any case, a state can formally repudiate a treaty it has signed. On that reading, no state sovereignty is lost by signing a treaty.
An example of no comeback is the recent ruling of the Strasbourg court against the UK’s blanket penalty of losing the vote if you were in prison. This court comes from the Council of Europe treaty, which predates the EU and includes Russia. The court said that it was legal to deprive someone of the right to vote if the judge so decided on the facts of the case. Instead of changing British law to give discretion to the judge, the UK Parliament chose to reassert the blanket loss of voting rights for all prisoners. There has been, and can be, no comeback. So in this case, the sovereign parliament used its power to override a supra-national court, to whose jurisdiction the Crown had signed up in a treaty.
The second lawyer view is that a treaty pools sovereignty on those issues it deals with. This is a point commonly made about the EU treaties. That is because they agree what the member states will work together on. The same argument would also apply to the NATO treaty, which is about pooling sovereignty for defence. This treaty contains a commitment to come to the aid of any member state which has been invaded or attacked by a third party. I have not heard anyone from the Leave camp argue that we should leave NATO. Yet if they are serious about state sovereignty, the NATO treaty, because it concerns the state’s core function of defence, is a bigger infringement of UK sovereignty than the EU treaties.
There are two big lies in the Leave case. The first is that the EU is a state which is bigger than the UK and can impose its will on us. The EU is not a state, but a treaty organisation. We agreed the treaties, and under them have voting rights in the Council of Ministers to decide on individual issues. Most decisions are taken by consensus. In the minority of cases where there is a vote, the UK has been on the winning side more than 85% of the time in the last five years. In the real world, negotiation results in an acceptable outcome, but not exactly what each individual wanted. The EU belongs to the real world, not the Leave fantasy.
The second lie is that the UK has no control over the future development of the EU. In particular it is claimed that the UK cannot veto any applicant to join the EU. But a new entrant is admitted through a treaty signed and ratified by every existing member. That means the UK has a veto as long as it is a member state. The UK has supported Turkey in the past, but in its present disregard for democracy it does not meet the requirements of membership.
The governments of many member states have the bad habit of wanting Brussels to take necessary but unpopular decisions. They vote for them in the Council of Ministers, and then announce to their national media that Brussels has forced them to do something. This habit is now coming back to bite us all.