The German National Library’s collection mandate is anchored in the Law Regarding the German National Library (DNBG) enacted on 22 June 2006. The Legal Deposit Regulation (PflAV), which is an integral part of the DNBG, contains supplementary regulations on applying the law. Both acts of legislation must therefore be considered together.

Law regarding the German National Library (DNBG)
(only available in German)

Regulation on the mandatory deposit of media works at the German National Library (PflAV)
(only available in German)

Along with the German National Library, the State Libraries in each federal state also have a regional entitlement to the submission of deposit copies. The conditions are regulated by the respective state government.

More about regulations in the federal states:
Pflichtexemplarregelungen in Deutschland 120kB, PDF - Barrier-free file
(only available in German)