Decisions of the Federal Constitutional Court shall be binding upon the constitutional organs of the Federation and of the Laender, as well as on all courts and those with public authority (cf. § 31 (1) of the Federal Constitutional Court Act). Generally, the binding effect relates to the matter decided in a particular case.
Certain decisions of the Federal Constitutional Court, in particular concerning the constitutionality of a legal provision, have the force of law (§ 31 (2) of the Federal Constitutional Court Act); they therefore apply beyond the individual case. They are published in the Federal Law Gazette (Bundesgesetzblatt).
Generally, the Federal Constitutional Court declares an unconstitutional law to be void. Voidness also applies retroactively, and, in terms of law, results in a situation as if the law had never been enacted. In certain cases, the Federal Constitutional Court merely declares a provision to be incompatible with the Basic Law and lays down a date from when on it may no longer be applied. This is done in particular if the legislature has several possibilities to eliminate the violation of the Constitution, or if the law immediately ceasing to be in force carries greater disadvantages than the disadvantages of it remaining in force for a limited period of time. This is often the case with tax laws, because the legal basis for levying a tax would be completely or partially abolished. In the transitional period, the legislature can enact a constitutional provision. In rare cases, the Federal Constitutional Court itself lays down transitional provisions.
Beyond the particular proceedings, the voidness of a legal provision voids all other decisions taken on its basis (cf. § 79 (2) of the Federal Constitutional Court Act). Decisions which can no longer be challenged remain effective but may no longer be executed. A further-reaching rule applies to criminal proceedings because of their drastic effects: if a criminal judgment is based on a legal provision that is void or incompatible with the Basic Law, the proceedings can be reopened even if the judgment has become final.