What is the ECJ and why is it such a problem?

The Luxembourg-based court of justice of the European Union is the highest court in Europe. Panels of judges from member states sit to interpret whether EU law is being fairly applied and can issue binding rulings over national courts.

The ECJ has had a relatively benign history with the UK – unlike the more contentious European court of human rights in Strasbourg – but nonetheless became a symbol of compromised sovereignty during the Brexit referendum. The EU has insisted that any future agreements on citizens’ rights and access to the single market must continue to be policed by the ECJ.

How does the UK plan to get us out of it then?

Much like its plan for retaining the benefits of the customs union or judicial cooperation in civil cases, the government hopes to fudge the issue by formally leaving the existing arrangement but recreating a very similar one in future. It might be called a tribunal, a committee or even court. It might consist of judges from Britain and the EU, and it might have the power to issue rulings that contradict UK courts.

However, since these rulings would have to be acted on by parliament rather than automatically overriding British judges, it would have only an “indirect” jurisdiction. The UK could refuse to comply, though it would face retaliatory sanctions or risk the whole divorce agreement falling apart. The only realistic option to defy future rulings might be to walk away entirely – a bit like Brexit was supposed to be.

How has this worked out for other countries?

The UK has outlined a series of precedents in its policy paper in order to demonstrate that there is no need for a third-party country, such as post-Brexit Britain, to submit itself to the authority of a foreign court in order to strike international agreements. While alternative arbitration mechanisms have worked well in the case of limited trade deals such as those between the EU and Canada or Singapore, they all involve some sovereign compromise in order to function.

The more extensive deals, such as those with European Economic Area and European Free Trade Association (Efta) members such as Norway or putative EU members such as Moldova, tend to have an explicit mechanism for the ECJ to step in. Brexiters are appalled by the UK’s example of Moldova because it requires an arbitration panel to refer questions of the EU law to the ECJ and “be bound by its interpretation”.

Should remainers be as alarmed by signs of compromise?

If you believe Brexit could involve Britain having all the benefits of EU membership without any legal responsibilities, then the past couple of weeks have been an eye-opener. If you think the ECJ is an effective bulwark to protect the rights of citizens and works well alongside national courts, this turn of events is perhaps less threatening.

The key question is whether government compromise can help unlock progress on other fronts in the Brexit talks. Outright rejection of the ECJ was a block to everything from regulatory cooperation to customs and trade. Some in the EU have indicated privately that accepting an alternative such as the Efta arbitration court could be enough. Others may regard this whole episode as more evidence that the UK has still not come to terms with what Brexit really means.