Germany's highest court on Tuesday overturned a law allowing authorities to retain data on telephone calls and e-mail traffic for help in tracking criminal networks.
A law ordering data on calls made from mobile or landline telephones and e-mail exchanges be retained for six months for possible use by criminal authorities violated Germans' constitutional right to private correspondence, the Federal Constitutional Court ruled.
In its ruling, the court said the law failed to sufficiently balance the need for personal privacy against that for providing security.
"The disputed instructions neither provided a sufficient level of data security, nor sufficiently limited the possible uses of the data," the court said.
Nearly 35,000 Germans had appealed to the court to overturn the law, which stems from a 2006 European Union anti-terrorism directive requiring telecommunications companies to retain phone data and Internet logs for a minimum of six months in case they are needed for criminal investigations.
The court upheld the EU directive, saying the problem lay instead with how the German parliament chose to interpret it.
Under the German law, which went into effect in January 2008, information about all calls from mobile or landline phones was retained for six months, including who called whom, from where and for how long.
The following year, that law was expanded to include the data surrounding all contact via e-mail.
Although the laws forbid authorities from retaining the contents of either form of communication, they met with fierce opposition from civil rights groups.
"Massive amounts of data about German citizens who pose no threat and are not suspects is being retained," Germany's commissioner for data security issues, Peter Schaar, told ARD's morning show.
Experts argue the information is crucial to being able to trace crimes involving heavy use of the Internet, including tracking terror networks and pursuing child pornography.
The court ordered the law be revised.