The decision of the Federal Court of Justice in Karlsruhe bars police from using software to search through remote hard drives unless parliament passes a law explicitly allowing the technique. Police, however, still will be allowed to seize evidence from PCs when conducting searches in person.

Arguing that stealth searches were indispensable to investigating criminals and terrorists, Interior Minister Wolfgang Schaeuble, the country’s top security official responsible for police, called on the government to seek swift changes in the law.

"It is indispensable for criminal investigators to be able to carry out online searches secretly and with a corresponding order from a judge," he said in a statement.

The decision came in response to a request by the Federal Prosecutor’s Office, which had sought to use Trojan horse programs to investigate a possible terrorist group. Prosecutors argued the legal reasoning used to allow telephone surveillance and other electronic eavesdropping techniques should be applicable to gathering evidence over the Internet.

Although the decision produces difficulties in evidence collection, the prosecutor’s office welcomed the decision, saying it clarified the issue. Officials there also called for legislation enabling the remote searches.

Members of the opposition Left Party and Free Democrats said the court’s decision was a victory for civil liberties. (AP)