A law giving security services access to a centralised antiterror database has been ruled partially illegal in Germany.
The Federal Constitutional Court ruled the law was too vague about the conditions necessary for gaining access to intelligence on terror suspects.
The antiterror law also blurred the dividing line between law enforcement and intelligence that was established after the Second World War to stamp out the abuses of the Nazi period.
The court ruled there must be an "overwhelming public interest" and a "sufficient concrete danger" of an attack to justify certain information being passed from one agency to another.
Judges said the law must be amended to permit legal access to the antiterror database, which contains information on more than 16,000 people, including suspects and their contacts.
The information in the database includes names, dates of birth, addresses, bank details and religion, as well as registered weapons and "skills relevant to terrorism".
The disputed law allows authorities to perform systematic searches of the database to find connections between investigations and suspects.
The federal court ruled this can now only occur with "strong evidence of a suspected offence".
The 2007 law was initially aimed at Islamic extremists but was updated in 2012 to cover the far-right scene.
In 2013, the court received a similar challenge and decided that lawmakers must bolster civil rights protections.
The court ordered "transparency" measures and said that officials charged with protecting data privacy must be given a clear watchdog role in the operation of the database.
The ruling on Friday found that legislators had not gone far enough in ensuring those protections under a revision that went into effect in 2015.
Germany is facing a problem with the influence of the far-right, which has affected the military and police.
The country's domestic intelligence chief said the far-right was the biggest threat to national security.
