The case of Ralf Bader, rejected because he had English, not German, qualifications, could set a precedent for the recognition of qualifications between European Union countries.
Mr Bader did his A-levels at the private Abingdon school in Oxfordshire and applied for a prestigious European business course at Reutlingen university, Baden-Wuerttemberg.
He passed the entrance exam with flying colours and the university accepted him. But Baden-Wuerttemberg state, which checks admissions, decided his A-levels were not equal to the German school-leaving exam, the Abitur. It said he had studied for only 11 years rather than the 12 required for the Abitur and had no qualification in English, a compulsory part of the Abitur.
However, non-Germans can qualify for university entrance in Germany by doing A-levels and gifted pupils skip a year or even two to take the Abitur early. Now, after a two-year battle, a Stuttgart court has accepted Mr Bader's plea that under EU rules, a German student cannot be treated worse than a student from elsewhere in the EU.
After being rejected, Mr Bader spent a a year at the Sorbonne, before being accepted by Oxford university to read philosophy, politics and economics.
Mr Bader's father, Johann, a judge who took up the case on behalf of his son, said that in Germany university is free, but the family has had to pay fees and maintenance at Oxford. He blamed a "coterie of out-of- touch bureaucrats" for the mistake. They had no understanding that students might want to mix courses and experience education elsewhere, he said.
The German state's education minister, Annette Schavan, who became aware of the case only recently, has been active in trying to promote student mobility within the EU.
After the ruling, Ms Schavan admitted the laws in her state were "not appropriate to our times" and pledged that overseas qualifications would be treated with greater flexibility in future.
Mr Bader was awarded costs. Now in his second year at Oxford, he is unlikely to reapply to Reutlingen. His father is considering claiming back the cost of sending his son to Oxford from the German authorities.