The European Court of Human Rights (ECHR) on Tuesday issued an interim measure asking the government of Russia to release political activist and opposition leader Alexei Navalny, who was recently sentenced to three-and-a-half years for violating his parole. The ECHR’s ruling was rejected by Russian authorities, including the Minister of Justice and the Press Secretary to President Putin.

The ruling, which was posted on Navalny’s website, instructs the Russian government to set Navalny free immediately and warns that failure to do so would mark a breach of Article 34 of the European Convention on Human Rights, to which Russia is a party. The court’s Seven Judges’ Chamber decided that “in the interests of the parties and due process,” Russia should release Navalny as per Rule 39 of the Court’s Regulations. The court took the decision for immediate release, citing “the nature and extent of risk to the applicant’s life” and the “overall circumstances of the applicant’s detention,” which prima facie met the purpose of an interim measure.

In a statement to the Tass News Agency, Russia’s Minister of Justice, Konstantin Chuychenkoa, was quick to respond, claiming that the ECHR’s demand was unprecedented and impracticable because it has no legal basis. He further claimed that the court was blatantly interfering with the judicial power of a sovereign state and that the demand is ungrounded and unlawful because it does not contain a single fact or a single legal norm that would make it possible for the court to hand over such rulings.

Navalny is an anti-corruption investigator and President Vladimir Putin’s most prominent critic. He was arrested last month upon returning to Russia for violating the terms of his probation while recuperating in Germany from nerve-agent poisoning that he has attributed to the Kremlin’s agents. The Moscow court that sentenced reasoned in its judgement that Navalny would need to serve two years and eight months of the sentence because he had already served one year of his sentence under house arrest in 2014.

Last year Russia adopted a constitutional amendment declaring priority of national legislation over international law. According to the amendment, the decision of an interstate body shall not be enforced in Russia if the decision at issue is based on an interpretation of an international treaty that contradicts the Constitution.