For the first time in the history of the European Union's Court of Justice (ECJ), which deals with cases concerning competition and antitrust, one of its judges will be a former head of the EU's competition department, raising the spectre of conflicts of interest in the powerful EU court.

Johannes Laitenberger, a highly respected German lawyer who has led the competition department since 2015, is expected to join the EU's General Court as a judge in September, provided he is nominated by the German Government and approved by the other 27 members of the EU.

The General Court, the lower of the ECJ's two courts, deals with competition cases as well as other commercial issues such as intellectual property. The General Court's judgments can be appealed in the higher court, the Court of Justice.

The plan to appoint as a judge an official who has been in charge of several high-profile antitrust and state-aid cases during his term, has become a hot topic in EU legal circles because of the potential for conflicts of interest.

Laitenberger will have to recuse himself from several cases if commission decisions that he has worked on are brought before the court. At the same time, Laitenberger is highly regarded for his legal expertise, so lawyers dealing with EU law are welcoming his arrival at the court.

"Recusal is a pain. But it's a trade-off for his experience," said Stephen Kinsella, head of Sidley Austin's EU competition practice.

During his term as director general of the commission's competition department, Laitenberger worked on the decision to block the merger of train companies Alstom and Siemens. Laitenberger's political boss, Margrethe Vestager, rejected the companies' plans despite fierce political pressure from the French and German Governments. Laitenberger was also in charge when the commission blocked the planned merger of stock exchanges, Deutsche Boerse and LSE.

There are precedents for senior officials from parts of the EU's administration moving to the Court of Justice. Allan Rosas, a Finnish judge at the Court of Justice since 2002, was deputy head of the commission's legal service.

José Rivas, a partner at Bird & Bird's Brussels office, said the tendency to recruit senior officials to the court does not generally pose a problem. The EU's court of justice has rules to avoid potential conflicts of interest, he said. Judges can request that they not take part in a case where there could be questions about their impartiality. Crucially, parties themselves can ask for a judge to step down from a case if they have concerns about independence.

"Is this an endemic problem which can't be addressed? No, I don't think so," he said.

Nevertheless, Laitenberger has been in charge of the commission's competition and state-aid decisions since 2015 and he will likely be a judge at the court that deals with those cases.

Kinsella said "it's extremely unusual" to have a senior competition official moving to a judicial role at the court – "particularly as it's part of the commission that generates so many of the important cases that come before the court".

In 2018, the General Court handled 70 cases related to competition and state aid, out of a total of 732 cases.

While Laitenberger is expected to recuse himself from cases he dealt with, the effect will be partially offset by the benefit of having his knowledge at the court's disposal, Kinsella said. "I think Laitenberger's appointment is a good thing. He's got real case experience."

Bird & Bird's Rivas shares this positive assessment. "His professional qualities are irrebuttable," he said.

Still, the fact that the court has relatively few practitioners among its members with extensive experience in EU law is seen as a shortcoming.

Most judges in the General Court are either national judges with limited experience of EU law, or law professors or national officials, according to Rivas. Marc Van der Woude and Ian Forrester, Dutch and U.K. members of the court, stand out as lawyers with significant experience in private practice.

"What would be better is if there were as many judges coming from the EU bar." Rivas said.