The European Court of Justice has ruled on an illegal state aid case, which could shed light on the court's views ahead of the Government's appeal against the Apple tax decision.

Europe's highest court found in favour of the European Commission on an issue involving tax concessions for a group of companies, including Santander Bank.

The issues involved in the complex, long-running case are regarded as pertinent to the Government's appeal against the Commission's finding that Apple had benefited from illegal state aid through its tax arrangements with the Irish State.

However, the Government here has pointed out its grounds for appealing the Apple finding are different to the Santander case.

A spokesperson for the Department of Finance said: "It is a complete overstatement to say that the Irish appeal of the Apple Decision is dependent on the outcome of the Santander and Autogrill decision of the European Court Justice, or that today's judgement is crucial for the Irish case."

At issue is a tax concession introduced by the Spanish government, which favoured companies that had a 5% shareholding in a foreign company.

The European Commission investigated the issue following complaints by a number of Spanish MEPs who argued the tax concession discriminated against companies that did not have a similar shareholding.

The Commission found the concession represented illegal state aid and required the companies in question to repay the tax to the Spanish state.

Spain and three companies - Santander, Santusa and Autogrill (now trading as World Duty Free Group) - appealed the finding to the General Court of the European Court of Justice.

In November 2014, the General Court ruled the Commission had not shown that the companies in question had selectively benefited from the tax scheme.

Showing that a scheme is selective, i.e. that it favours one undertaking over another, is a key criterion for establishing that illegal state aid has taken place.

The General Court had found the Commission had failed to identify a category of undertakings, or commercial operations, that was exclusively favoured by the tax measures.

The General Court annulled the Commission's findings in the case.

However, the Commission appealed that ruling to the European Court of Justice, the higher court.

Today, the ECJ ruled the lower court had erred in law in reaching its ruling that there was no selectivity involved.

The court ruled the Commission simply had to show that some companies had benefited over others that were in a similar factual or legal situation in order for selectivity to be established.

Judges concluded the Commission did not have to identify a particular category of company that exclusively benefited from the scheme.

The Court declared the lower court had erred in law in finding that the tax schemes operated in Spain were not selective, and therefore not discriminatory.

Ireland was one of only two member states that made written and oral submissions to the Santander case, with senior counsel arguing the scheme in Spain had not selectively benefited the companies involved.

It is understood the Government supported the view that it was difficult, if not impossible, to prove a scheme selectively benefited some companies over others, since this would be one of the key arguments in its defence of the Apple decision.

However, the judgment provides fresh case law showing the European Court of Justice takes a sympathetic view of the Commission's interpretation of how tax schemes can constitute illegal state aid.