The European Court of Human Rights (ECtHR) ruled Tuesday that Italy has failed to protect the private and family life of cohabitating same-sex couples by not allowing for any legal recognition of same-sex relationships. The ruling does not demand that Italy recognize same-sex marriages. Still, the potential effect of this decision is huge. The Court argues that not having a law that recognizes same-sex relationships is a human rights violation. The ECtHR has jurisdiction over more than 800 million people in 47 countries, 23 of which do not have any form of registered partnership for same-sex couples. Potentially, this ruling affects all these countries. But the effects are not direct and may not materialize any time soon. Below is a quick explainer.

What is the European Court of Human Rights?

The ECtHR was established in 1959 to interpret and enforce the European Convention on Human Rights. Gradually, the membership of the Court has grown to include all countries in Europe other than Belarus, but including Russia and Turkey. Almost all cases involve an individual who alleges that their government has violated  the Convention. The Convention includes an article (8) that protects an individual’s “private and family life.” By now, the Court has issued almost 50,000 judgments, the bulk of which have come since 1999.

What happens when the European Court of Human Rights finds a violation?

A judgment is binding on the member state against which it was issued. Yet, unlike with U.S. Supreme Court rulings, judgments are not always implemented; at least not immediately. An ECtHR ruling cannot directly invalidate a law. The cabinets, parliaments, and courts of countries must take actions. However, the ECtHR has some leverage. For example, the three couples in the Italy ruling will receive modest monetary compensation from the Italian state. The Court is sure to rule the same way for other individuals who sue Italy. Still, it may take some time before we see legislative reform, especially on a controversial issue like this. Moreover, Italy may appeal to the Grand Chamber of the court. That is what Italy did successfully in 2011 after the ECtHR had initially (unanimously) ruled that the requirement that crucifixes be displayed in Italian classrooms of state schools was a violation. In that case, Italy relied on considerable support from other states where religion plays an important role in public life or who were otherwise upset with the ECtHR.

But aren’t Europeans incredibly progressive on LGBT rights anyway?

Well, it depends which Europeans you are talking about. In many Eastern and Southern European countries public acceptance of homosexuality remains as low as anywhere in the world. The graph below illustrates this based on data from the World Values Survey has asked respondents in each of its waves to rate on a scale from 1 to 10 whether homosexuality is “justifiable,” where 1 means “never” and 10 “always.” In the graph, dots with darker colors represent more recent surveys. For most countries, the darker dots are to the right (greater average acceptance) of most or all of the lighter dots. But there are many countries that have barely moved and where there has been considerable backlash against LGBT rights. Italy is somewhere in the middle. It is just about the most progressive of the 23 countries that do not have any formal recognition of same-sex partnerships. So, if the judgment is going to be controversial in Italy, it will likely be controversial elsewhere.

How does the judgment matter for other countries?

The ECtHR resolves individual cases. Other countries have a right to wait until a formal case is brought against them and to argue in front of the court that their domestic situation differs from that in Italy. Nevertheless Larry Helfer and I showed in an article published in the journal International Organization that on average countries become much more likely to change domestic laws after a ECtHR judgment found violations in similar laws elsewhere. This can be so for a myriad of reasons. Governments expect to lose similar cases at the ECtHR. Domestic courts may start using the ECtHR’s interpretation. Or elites who were already favorably disposed towards policy change but who faced domestic opposition may use the judgment to advance their cause.

Still, this research used issues of discrimination and decriminalization, which tend to be less controversial than partnership rights. Moreover, it is based on a period when the backlash against LGBT rights, especially in Eastern Europe, was much less pronounced than it is today. It is by no means clear how far reaching the consequences of Tuesday’s judgment will be.