Mobile Code (MC) technologies provide appealing solutionsfor the development of Internet applications.For instance, Java technologyfacilitates dynamic loading of application code Pom remote servers into heterogeneous clients distributedall over the Internet. However, executing foreign code that has been 1oadedfi.omthe network raises signixcant security concerns which limit the diffusion of these technologies.Substantialwork has alreadybeen done to provide security solutionsfor protecting both hosting nodes and mobile code. For example, the Java security architectureevolvedfiom a rigid sandbox model to a more flexible solution where downloaded code canperform any kind of operations, depending on its source location and signature. However, the most widespreadsecuritysolutions for MCplatforms today do not support the sophisticated security policies required in modern inter-organisational environments. This requires expressive languages to specifi the policy and flexible mechanisms for po...