The AIVD secret service may not tap lawyers’ telephones unless it has been given permission by an independent body, a court in The Hague said on Wednesday.

The court ruled that the AIVD has six months to officially change its current practices and warned that if the AIVD does not comply, it will be banned from tapping lawyers’ phones altogether.

The case was brought by criminal law firm Prakken d’Oliviera, which discovered last year that the AIVD had been listening in to conversations since 2003.  The security service regulator has already said some of the phone taps were illegal.

The law firm’s clients include Volkert van der Graaf, who murdered politician Pim Fortuyn and suspected terrorists, making them an interesting target for the AIVD.

The court said an independent organisation needs to be established to ensure the AIVD is keeping to the law and to decide if recorded conversations can be passed on to the public prosecution department.

The current system, in which the legality of taps is checked after they have been carried out, is illegal and infringes upon the right of lawyers to have confidential conversations with clients, the court said.