Artikel 13

1. Except where expressly provided otherwise, international agreements or other provisions in force in the Federal territory concerning social security, including social and medical assistance, shall not apply to members of a force or of a civilian component or to dependents. However, rights and obligations of such persons in the field of social security which have arisen during previous presence in the Federal territory remain unaffected. Furthermore, the fact that a person belongs to one of the categories referred to in the preceding sentences shall not preclude the possibility of his paying contributions to the German social security (soziale Kranken- und Rentenversicherung) for the purpose of continuing insurance on a voluntary basis (Weiterversicherung) nor the possibility of his acquiring and asserting rights deriving from existing insurance.
2. Nothing in this Article shall affect the obligations of a member of a force or of a civilian component or of a dependent in the capacity of an employer.