Access control is one of the key requirements in enterprise security. A number of approaches in distributed systems have been designed that support various (new) paradigms such as peer-to-peer, nomadic working, and teamworking. Few of them, however, explicitly take into account the possible superposition of these concepts. Such a superposition often results in conflicting and additional requirements. We present ongoing work in developing an access control system for Peer-to-Peer mobile teamwork environments. This system is developed as part of the MOTION project. The goal of this project is to develop a service architecture for mobile teamwork, providing support for various devices and taking into account diverse connectivity modes. We present the requirements for an access control system that simultaneously supports mobility, collaboration, and peer-to-peer, illustrate our solution, and discuss how it meets the requirements.