Although several access control policies have been proposed for securing access to resources, they focused on security of distributed environments that were rather static. Nowadays distributed environment becomes open and dynamic. In this paper, we propose a formal language for access control policies in open and dynamic environment. The language is based on description logic program and generalized courteous logic program supporting classical negation, prioritized conflict handling and mutual exclusion constraints. The language allows the specification of positive and negative authorization, privilege delegation and revocation, prioritized conflict resolution and mutual authorization exclusions.