The Federal constitutional Court on Tuesday upheld a complaint by the opposition Green party, which said Parliament was not informed early enough about the details of the European Security Mechanism. Party leaders say they obtained details from their sister party in Austria.
The decision has no bearing on the future of the ESM itself, on which Parliament is expected to vote next week. But the court made clear that in future Parliament must be in a position to have "early and effective influence" on government decisions.
The ruling is the latest of several which have strengthened Parliamentary rights.