Part 4 Mutual Assistance through the Execution of Decisions and Orders of the Court
§ 41 Enforcement of Prison Sentences
(relating to Article 77 para. 1,Article 103 para. 1 and 2, and Articles 105, 106, and 110 of the Rome Statute)
(6) Costs arising from the enforcement shall be borne by the federal government in accordance with an agreement to be entered into with the states (Länder). This does not apply to the extent costs are to be assumed by the Court pursuant to law or other regulations.
EDIT.