Subject to the relevant rules of Community law, each Member State may determine in which circumstances, and the extent to which, the costs of security measures taken under this Regulation to protect civil aviation against acts of unlawful interference should be borne by the State, the airport entities, air carriers, other responsible agencies, or users. If appropriate, and in conformity with Community law, Member States may contribute with users to the costs of more stringent security measures taken under this Regulation. As far as may be practicable, any charges or transfers of security costs shall be directly related to the costs of providing the security services concerned and shall be designed to recover no more than the relevant costs involved.