Catalan political prisoner and ERC leader Oriol Junqueras has appealed the decision of Spain’s Supreme Court to deny him permission to leave prison in order to take the necessary steps in Madrid to become a member of the European Parliament, and wants the issue to be solved by the Court of Justice of the European Union, based in Luxembourg.

Junqueras lawyers urged Spain’s top court to “temporarily suspend” the ban and file a series of “prejudicial questions” to Luxembourg to determine whether or not the decision to not allow him to take up his seat contradicts European law. All MEP-elects are expected to attend Spain’s congress on June 17 in order to swear an oath to the constitution, a step considered “mandatory” by Spanish authorities to officially become EU parliament members.

Yet Spain’s Supreme Court refused to allow Junqueras out of jail to attend the event. Last month, the same judges gave him temporary permission so he could become an MP in Spain’s congress. The Court now argues that allowing Junqueras to become an MEP would pose an “irreversible danger” on the proceedings against him.

However, Junqueras lawyers argue that the decision violates the leader “fundamental rights”, especially his right to political activity, presumption of innocence or freedom of speech. That is why they asked the Court to “urgently” file a prejudicial question to Luxemburg, that should rule on whether is it legal to forbid an elected politician from effectively taking his post by keeping him in preventive prison.