Security policy allows the administrator to restrict the permissions granted to code running on the machine. The policy system looks at evidence about all managed code – where it comes from, name or publisher identity, and so forth – as the basis of a trust decision about the code, that results in a set of permissions the system is willing to grant the code. Security policy may be configured at the machine and user levels in the Tech Preview.
The details of how to configure security policy are given in Runtime Code Access Security Administration.