A political crisis is bubbling away in Europe about the abuse of law for political ends. The casus belli is a deal struck by Pedro Sánchez, the Spanish prime minister, with the Junts, the Catalan independence party led by Carles Puigdemont, ahead of this week's investiture vote. The events have the potential to radiate far beyond Spain. They might even scupper the EU accession of an independent Scotland.

The core element of the deal between Sánchez and Puigdemont is an amnesty law for Catalan leaders. This is not something that a parliament should normally be able to decide on. Didier Reynders, the European justice commissioner, wrote a letter to the Spanish government, expressing alarm at the idea of a political amnesty overriding a legal ruling by an independent judiciary. The Spanish opposition agrees with Reynders. But everybody is doing it these days - interfering in legal processes.

When interviewed by David Frost, Richard Nixon famously said: “Well, when the president does it, that means that it is not illegal.” The Spanish amnesty law has a Nixonian quality to it. The deal would grant amnesty for Catalan leaders who were convicted of sedition after the 2017 independence referendum. It would also lift the arrest warrant for Puigdemont. He was president of Catalonia at the time of the referendum. The Yes vote won an overwhelming victory, on a small turnout. It triggered a fierce reaction from the Spanish authorities - again a case of politicians instituting legal proceedings. Puigdemont fled the country in an infamous car chase as part of which he changed cars under a bridge. Today, he is a member of the European Parliament, and has not been back to Spain since.

The EU’s three-year old rule-of-proceedings give the European Commission the right to interfere in the politics of a member state if the Commissions suspect a breach of European law. The Commission has always been the guardian of European law, but lacked effective rights of enforcement. The Commission has not adopted a rule-of-law procedure against Spain. We are still in the letter-writing stage. The EU now faces the dilemma between following its own rules and frustrating the formation of a government of a large member state. It would also risk frustrating the opportunity of a political solution to the Catan conflict.

The main weapon of the EU rule-of-law procedures is the right to withhold payments from the EU budget. This is not a legal procedure, as the name would suggest. It is a political one. The European Commission first takes a decision. Then it puts the issue to EU ministers for a vote. They can block this decision if they find a sufficiently large majority. The intent is to protect judiciaries against politics - but it is politicians who trigger the procedure.

It was designed for what the EU deems to be rogue governments, like those in Poland and Hungary. EU law breaches are, however, not the exclusive domain of rogue governments. EU member states have different judicial traditions. The outgoing Polish government, run by the Law and Justice party, subjected its judges and justices to disciplinary procedures that were clearly not compliant with EU law. Viktor Orbán, the Hungarian prime minister, has gone much further than Poland in his suppression of freedom of speech and the subjugation of the legal system. Spain, by contrast, is a stable democracy. It is one of the pillars of the modern EU. Yet Spanish governments also have a history of mistreating their independent judiciary. In particular they failed to renew the mandate of the 20-member general council of the judiciary, the body that appoints Spanish judges and that ensures the judiciary's independence. That mandate ran out five years ago. The European Commission has called on Spain to renew the council's mandate - to no avail.

The Spanish political mess raises important dilemmas: will the Commission be as tough on Spain as it was on Poland, for example? If yes, is the EU ready to provoke a political crisis in a large member state? If no, the EU would risk standing accused of hypocrisy by applying rule of law proceedings against political opponents only.

I don't think the rule-of-law fanboys thought this through. Angela Merkel was sceptical from the beginning. What the rule-of-law crowd always underestimated was that those under attack would strike back. Orbán is now blackmailing the EU by linking a resumption of EU budget payments to the release of financial aid for Ukraine. How can you discipline member states if you rely on them for your foreign policy?

Spain would have significantly greater resources to blackmail the EU if the EU were ever to get serious and try to block the formation of a new government on legal grounds.

Separately from all this, the conflict also has implications for the EU's position on independence movements elsewhere. In Scotland, there has been a lot of complacency about the possibility of EU membership after a hypothetical Yes vote in an independence referendum. There is no shortage of people in the EU who would support Scottish EU membership.

But they, too, did not think this through. A Spanish government cannot conceivably agree to the accession of an independent Scotland while denying the same right to Catalans. That is especially the case now that Spain and Catalonia put their past conflicts behind them.

The EU cannot be simultaneously hostile to Catalonia and friendly towards Scotland. Nor can it condone law breaches in some parts of Europe, but not in others. It cannot be hostile to Orbán, while allowing Sánchez to override the Spanish judiciary. These are all self-inflicted dilemmas.