Since 2009, the Federal Criminal Police Office has had powers such as bugging homes of suspects, tapping phones and installing surveillance cameras. A former interior minister and several other opposition politicians challenged the new rules.
The Federal Constitutional Court ruled that those powers are largely in line with the constitution but the way they are defined doesn't always respect the "need for proportionality" and is sometimes too vague.
The court also said that for the data gathered to be transferred to authorities in a country outside the European Union, it needs to be clear that the country will use the data in a way that is acceptable in terms of human rights and data protection.
Interior Minister Thomas de Maiziere said the government "accepts and respects" the ruling, though some of it "doesn't make the fight against international terrorism easier."
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In particular, Germany's exchange of information with international partners "must be preserved, even expanded," he said.
"There has to be a minimum standard, of course, and we have to attach importance to no abuse being committed with data when we pass it on what that means in detail, we will have to discuss," de Maiziere said.