Who's right, David Cameron or Michael Gove?

Is the EU renegotiation deal which David Cameron agreed last week legally binding? It’s an important point, as the exact legal status of the deal is the subject of dispute between Michael Gove (backing the Leave side) and Cameron (backing the Remain side), along with the Solicitor-General. As with many legal questions, there isn’t a simple "Yes" or "No" answer, but a nuanced one.

Furthermore, the answer depends on which part of the deal you look at. There’s a main part of the deal, concerning sovereignty, financial regulation, and competiveness. But there’s also a separate decision which will let the UK delay (but not veto) draft EU laws on financial regulation. And there’s an agreement to pass three future EU laws: curbing child benefit exports, limiting in-work benefits for EU migrant workers, and making it harder for EU citizens (and returning UK citizens) to bring in their non-EU family members – even if their marriages are long-standing and genuine.

At the summit, EU leaders explicitly stated that the main part of the deal was "legally binding". That’s normally enough in international law, and indeed the UK government intends to register the deal with the United Nations as an international treaty. But that’s not the end of the story, because the underlying dispute is about the enforceability of the deal. Many international treaties are hard to enforce; is this one any different?

The key point here is what happens if the main deal conflicts with existing EU law. In that case, the EU court has said that it will take decisions like these into account when interpreting EU law. But they don’t amend EU law as such. So if push comes to shove, EU law takes precedence over this deal, where there’s a conflict.

This leads us to the next question: are there any conflicts between the main deal and EU law? On some points, there’s definitely no conflict: as the deal says, existing EU law gives the UK an opt-out from the single currency, from Schengen, and from EU immigration, asylum and criminal law. On other points, though, it’s an open question if the deal interprets EU law correctly. For instance, there’s no case law on the "national security" exception in the EU Treaties. The deal says that this exception isn’t really an exception, and so Member States should have lots of leeway on this issue. While the EU Court might well accept that interpretation, and the deal probably makes it more likely that it would do, it doesn’t guarantee that it would.

What about the other parts of the deal? They would all take the form of ordinary EU law, so the question of conflict with other ordinary EU laws wouldn’t arise at all for them. But there might be other legal or political issues. The new law about delaying voting on EU financial services regulations should be the most secure, as it can be adopted by EU ministers alone without the European Parliament or Commission getting involved. It won’t affect individuals, so they couldn’t challenge it in court.

The three new laws on benefits and family members need the support of the Commission and other Member States, but that’s in the deal already. They also need the support of the European Parliament. The largest party there has said it supports the deal overall, but might quibble over the details. Some other parties will have to join them to get a majority. And after the laws are adopted, they might still be challenged by individuals via the national courts to the EU court, because ordinary EU laws can still be invalid if they don’t comply with the Treaties.

Overall then, Cameron and Gove are each about half right. The deal is legally binding, but its exact consequences are limited. On some points, it’s possible that the EU court might not agree with the interpretation of EU law in the deal. On other points, the deal might not be implemented, because the new laws might not be passed, or they might be successfully challenged. It comes down to whether the EU’s institutions can be trusted to implement the deal. If they don’t, then calls for another referendum (if there were a "Remain" vote) would likely grow – but knowledge of that fact might in turn encourage the EU institutions to stick to the deal.

For British voters, who have the final say on all this, whether they trust the EU on all this will probably depend on what they think of EU membership in the first place.