France's highest court ruled Tuesday that judicial phone taps between Nicolas Sarkozy and his main lawyer are legal, paving the way for an eventual corruption trial against the former French president that could hamper his bid for re-election.

Sarkozy is expected to seek the conservative nomination to run for president again next year.

The opposition leader is under preliminary charges of corruption and influence-peddling based on information gleaned from judicial phone taps in 2013-2014.

It is one of several legal cases in which his name has appeared, but the most potentially damaging to his political future.

His phones were tapped as part of an investigation into suspected illegal financing of his successful 2007 presidential campaign. But conversations heard via the phone taps brought to light a completely new legal case.

Sarkozy's lawyers argued the wiretapping was carried out in breach of lawyer-client privilege. But the Cour de cassation rejected their arguments and ruled that the investigating judges didn't break any laws when they secretly ordered to tap Sarkozy's phone.

The ruling means the investigating judges can go on with their investigation in the new case and eventually send Sarkozy to trial for corruption and influence-peddling. However, when they close their investigation, they can also decide to change the charges or dismiss the case altogether.

"It's not just disappointment, it's incomprehension," Patrice Spinosi, lawyer for Sarkozy in the top court case, said after the decision. "The ruling is a defeat for the defense rights" and may "lead the European court of human rights to sentence France over it."

The lawyers for Sarkozy will still have an opportunity to contest parts of the ongoing investigation, but only on different grounds than the lawyer-client privilege. They can also appeal an eventual order to send their client to trial.

In the wiretapping case, Sarkozy is suspected of trying to bribe a top judge for information about himself, covered by judicial secrecy. In exchange, the former president allegedly promised to use his influence to get the magistrate a prestige position in Monaco.

The opposition leader is expected to face a tough conservative primary later this year, with nine candidates in his party already declared and polls showing him as a runner-up. Even if any trial is not held before next presidential election in spring 2017, a suspicion of corruption and influence-peddling could be a hurdle in his presidential bid.

While his name has been mentioned in many legal cases since 2010, Sarkozy has never been convicted of wrongdoing or been sent to trial. Last month, he was handed preliminary charges for suspected illegal overspending on his failed 2012 re-election campaign.