The UK dropping our EU treaty commitment to "ever closer union" would make us less likely to be drawn into a federal Europe.
Unlike opt-outs in specific areas of EU activity, this change wouldn't have a direct legal effect. Any impact would be mainly political.
"We want an end to our commitment to an 'ever closer union,' as enshrined in the Treaty to which every EU country has to sign up."
"If 'ever closer union' were abandoned as an objective, the consequences would be serious."
Roger Bootle, City A.M., 4 June 2015
"People in Britain … do not want to be part of an ever-closer union to be dragged into a state called Europe. That may be for others, but it will never be for Britain, and it is time to recognise that specifically."
David Cameron, 26 June 2015
Two hundred years after a future British Prime Minister went to Brussels to settle the political direction of Europe, David Cameron was in the same city to formally present his aims for renegotiated EU membership. His plan relies on more words and fewer bayonets than Waterloo. Three words in particular, from the EU treaties, are said to be important: "ever closer union".
But are they significant? Put another way, would disapplying them from the UK—as Mr Cameron says he wants to do—really make much difference?
Not an opt-out from any particular laws
The changes Mr Cameron is seeking on ever closer union are sometimes referred to as an opt-out. This is a little unfortunate, as it implies that some EU laws will not apply to the UK as a result of this action. That isn't the case.
The EU is allowed to pass laws only on subjects that the treaties, as interpreted by the EU court, allow it to. For instance, the law on fair competition between companies is an EU area because it says so in the treaties signed by all the members. Competition law is an exclusive EU 'competence'.
An 'opt-out' usually refers to a situation where an EU competence doesn't extend to a particular country. That, too, is only because an exception is written into the treaties (after negotiation).
The UK has got an opt-out on laws passed under the EU competence in 'freedom, justice and security'. This includes things like criminal justice and asylum—which is why we wouldn't have had to take a quota of refugees if that idea had come to pass.
The three references to "ever closer union" in the treaties don't create any particular competence; nor do they mean that the EU has to keep expanding its powers over time, or can't be stripped of them. It's not a case of opting out from this concept in order to escape the reach of future laws created under it.
Some impact in the courts
It has been argued, though, that the phrase matters in the EU court. The idea is that when the judges come to make decisions on the EU's centralised power under the treaties, the reference to "ever closer union" helps them justify conclusions that expand that power.
The House of Commons Library looked into this recently, and pointed out that this rarely happens directly. The EU court has only ever cited the phrase "ever closer union" 54 times, and even fewer of those are final judgments (some appearances are in preliminary, though influential, opinions by an Advocate-General).
Even when it does appear, the judges are sometimes focused on the full phrase "ever closer union among the peoples of Europe, in which decisions are taken as openly as possible and as closely as possible to the citizen", in the context of public access to official documents.
The academic Gunnar Beck has argued that while the phrase itself is rare, the court has hundreds of times referred to the "spirit" of the treaties or individual laws, which he says amounts to "ever closer union". That sense of an over-riding objective gives the court a tendency to "favour or enhance further European integration" in its decisions.
A matter of politics and symbolism
If that's true, removing this phrase from the treaties, or stating that it can't be invoked in cases involving the UK, could send a message to the court—and the other EU institutions—that leads to changes in behaviour.
Then again, the treaties have plenty more general rhetoric where that came from. They talk about "a new stage in the process of European integration"; "further steps to be taken in order to advance European integration"; of "solidarity" and "convergence". The court, Commission and other EU bodies could take the view that the spirit of European integration isn't necessarily confined to one phrase.
Mr Cameron, though, may agree with people like Roger Bootle that a sense of inexorable political momentum towards a more centralised EU is created by the particular phrase "ever closer union". It may, on its own, be largely symbolic, but that's not the same as unimportant.
Whether or not a treaty reference to "ever closer union" gives European politicians a mandate, mission or tendency to pursue integration further than they otherwise would is impossible for us to say. What we can be quite sure of is that removing it isn't going to give rise to immediate, concrete change in how the EU or the UK work. The Prime Minister is playing for less tangible stakes, over a longer term.