Are the decisions of the European Court of Human Rights (ECtHR) are legally binding to the UK courts?

Yes, the decisions of the European Court of Human Rights (ECtHR) are legally binding on the UK courts. The UK is a member of the Council of Europe, which is the institution responsible for overseeing the implementation of the European Convention on Human Rights (ECHR), and is therefore obligated to comply with the decisions of the ECtHR. The UK courts, including the Supreme Court, must take into account the decisions of the ECtHR when making their own decisions and must interpret the provisions of the ECHR in a manner consistent with the ECtHR's case law. However, the ECtHR's decisions are not directly enforceable in the UK courts, and it is ultimately up to the UK courts to determine how to give effect to the ECtHR's judgments in the context of domestic law.