Article 4
Enforcement
1. Subject to the conditions contained in this Agreement, the sentence of imprisonment shall be binding on Austria, which shall in no case modify it.
4. If no State is designated under paragraph 1, the sentence of imprisonment shall be served in a prison facility made available by the host State, in accordance with the conditions set out in the headquarters agreement referred to in article 3, paragraph 2. In such a case, the costs arising out of the enforcement of a sentence of imprisonment shall be borne by the Court.