National judges in EU member states cannot be banned from seeking guidance from the European Court of Justice, the ruling stated.
The European Court of Justice (ECJ) has ruled that EU law precludes any decision by a member state's supreme court.
The decision is the latest development in a dispute over the rule of law between Brussels and Poland and Hungary.
The case related to a Hungarian judge who sought advice from the ECJ about arranging interpreters for criminal trials.
The District Court judge had wanted to know how a Swedish language interpreter was selected for a criminal trial and whether the defendant had been fairly informed of their rights.
Hungary has no official procedure or registers for appointing translators or interpreters for legal proceedings.
But Hungary's Supreme Court placed the judge under disciplinary procedures and banned him from seeking guidance from the EU court.
However, the ECJ ruled on Tuesday that it was "prejudicial" to prevent the judge to seek independent EU court advice.
The Luxembourg court said the judge's question was "relevant and necessary" to the case he was hearing in Hungary and ruled in his favour.
"The principle of the primacy of EU law requires the lower court to disregard the decision of the supreme court of the Member State concerned," judges said.
"EU law precludes disciplinary proceedings from being brought against a national judge on the ground that he or she has made a reference for a preliminary ruling to the Court of Justice."
The EU court added that banning judges from seeking their advice could threaten "judicial independence".
Hungarian Prime Minister Viktor Orbán has previously been accused of curbing the independence of judges and threatening the rule of law.