A court challenge over the legality of the EU’s Brexit negotiations brought by a 97-year-old war veteran and 12 other emigrant Britons has been rejected by the European court of justice in Luxembourg.

Harry Shindler, who lives in Italy, and others who reside in various EU member states had argued that the referendum in 2016 was invalid because they and more than a million Britons living in the EU were deprived of a vote.

French lawyers acting for the British claimants said the EU should not, therefore, have accepted the UK’s intention to withdraw and start negotiations which culminated in the deal signed in Brussels on Sunday.

But the Council of the European Union opposed the application, arguing that the EU’s decision did not affect the applicants’ legal situation but was merely “a preparatory act”. Only when article 50 was completed, formalising the UK’s departure, were the rights of the applicants liable to be affected, it maintained.

The ECJ agreed, according to a statement issued by the court, that the “decision to open negotiations for an agreement with the UK … does not directly affect the legal situation of the applicants”.

It went on: “The [ECJ] therefore dismisses the action as inadmissible since the decision of the council authorising the opening of negotiations on Brexit does not produce binding legal effects capable of affecting the interests of the applicants by bringing about a distinct change in their legal position.”

Shindler, who was born in London and served in Italy during the second world war, took part in the 1944 liberation of Rome. He married an Italian and went to live there when he retired in 1982. He was awarded an MBE in 2014 for his services to British-Italian relations.

Before the court case, he said: “We are called expatriates but we are not all old or retired. We are journalists, interpreters, teachers and do all sorts of other jobs – we are representative of the general run of the British nation.”

There is a 15-year time limit on British emigrants being able to register as overseas voters. The government has said it will support a private member’s bill introduced by the Conservative MP Glyn Davies that would do away with that time restriction in future. Labour has refused to back the bill, saying it would involve too much administration.