I still remember my shock in the early 1990s when a colleague at the Times newspaper in London said to me that the eurosceptics were winning the argument. Up until that time, I thought of europhobes as British eccentrics, foul-mouthed and halitosis-ridden, and not to be taken seriously. They succeeded by setting the tone of the debate.

Twenty years of EU-related rulings by the German constitutional court had a similar effect. At no point did the court ever rule against an EU treaty or an EU policy. It was never the ruling that mattered, but the legal argument. In last year’s decision on ECB asset purchases, Karlsruhe famously attacked the Court of Justice of the EU of having gone beyond its mandate, or ultra vires. It also opined that member states had conferred clearly delineated powers onto the EU, but that sovereignty rests squarely with the member states. It is they who giveth, and they who taketh away.

In its ruling last week, Poland’s constitutional court went beyond anything the German constitutional court ever did. It declared Art. 1 of the Treaty on European Union, the clause that establishes the EU, not compatible with certain chapters of the Polish constitution. It found the same for Art. 19 TEU, which establishes the CJEU. If sustained, this would constitute a legal Polexit. If a member states believes that the EU treaties violate their national constitution, they either have to change the constitution, get the other members to agree to a change in the treaties, or leave the EU. The EU could, if it wanted to, even make an argument under international law that this ruling automatically voids Poland’s accession treaty, and thus its EU membership.

The role of the German constitutional court in all of this is indirect but nonetheless important. What it did was engage in a legal discourse that made the Polish outrage possible. Readers may recall that the CJEU was a big factor in the Brexit discussions. If only the remainers had known that they could have renationalised some of those powers? Despite the europhobia that led to Brexit, there was much less of a sense of secessionism in the legal profession, compared to with Germany or Poland.

The Polish court, by contrast to the courts in Germany and the UK, is staffed by political loyalists. The English translation of the ruling reads more like a political pamphlet than a legal text. The German constitutional justices are also appointed by politicians, but they represent a broad range of legal opinion. The anti-European prejudices did not arise from political interference but inside the legal profession itself. Lawyers, like economists, follow academic schools of thought that chime with their own political views.

Some of the arguments used during the Polish hearings were straight copies of arguments made by the German constitutional court. Karlsruhe, for example, popularised legal concepts such as ultra vires and the democracy principle. They sound more innocent than they are. Karlsruhe argues that sovereignty can be conferred but not shared. This implies that the CJEU cannot be the arbiter of its own remit. It also means that EU law does not override national law in areas outside the agreed perimeter, and that it is the national courts that decide the precise location of that perimeter. Karlsruhe, however, accepts the primacy of EU law inside the perimeter, like the single market or trade policy. Fiscal policy and defence are not part of that remit. So, if you want a fiscal union or a European army, you cannot do this inside the existing treaty. The next layer of European integration will not happen until member states agree to change the EU treaties and, in the case of Poland and Germany, the national constitution as well.

The Polish ruling will almost surely end up in Poland backing down. I see Polexit as a possible but improbable outcome. But remember that Brexit, too, started out that way.

The Karlsruhe version of legal euroscepticism has been far more clever, and more effective. It managed to create legal facts out of thin air that informed the EU negotiating position of successive German governments. The Polish ruling, by contrast, is drafted as a deliberate provocation that might play into the hands of Law and Justice ahead of the 2023 elections. Karlsruhe is not responsible for what is happening in Poland. But it is responsible for starting a discourse that others take up and push to the limits.