Websites that use Facebook Like are responsible for the data they send to Facebook and will of course be subject to the same penalties under EU privacy laws.
The decision was announced today for an earlier lawsuit launched in Germany by 2015, when Verbraucherzentrale NRW, a German consumer protection group, demanded that Facebook Like be banned from the Fashion ID page of a German online fashion store.
NRW argued that by integrating Facebook Like into its site, Fashion ID allowed Facebook to collect data from site visitors without their immediate approval.
The German team sued Fashion ID in a German court on 2015, in an effort to remove the button or make administrators ask for users' permission for the data sent to Facebook.
The case went smoothly, starting with a local court in Düsseldorf. He later went to the German Supreme Court in Berlin, which, in the absence of a previous convict, sought a formal opinion from the European Court of Justice (ECJ) last year before issuing a final ruling.
Opinion announced today (PDF) and according to the Supreme Court of Europe, any website that uses a Facebook Like button or the like is responsible for the user data that is collected and sent to third parties.
The WEU justified its decision by stating that Fashion ID had a direct commercial benefit from placing the Facebook Like buttons on the website it uses.
The European Court of Justice has ruled that the presence of "Like" buttons and data collected through the buttons allowed to increase the visibility of the company's products on Facebook.
Today's decision does not bind anyone. This is a formal opinion stating how the Berlin court can adjudicate its case. The Berlin court may - or may not - use it in its final decision in the Fashion ID case.
Of course, the opinion of other countries' courts will also be able to use this opinion to adjudicate similar cases.