How to remove full trust from assembly, which no longer exists on the disk?

Question

This particular "full trust" list has to do with participation in CAS policy decisions, not a more typical unrestricted permission grant, and it hasn't been used by the .NET Framework since v.2 was release. In other words, removing the assembly from the list should have absolutely no effect.

That said, if you really want to do this, caspol.exe has no option for avoiding the file load, so you would need another approach. You could, for example, call [PolicyLevel.RemoveFullTrustAssembly(StrongNameMembershipCondition)][1] from custom code. e.g.:

new FullTrustPolicyRemover().RemoveAssembly("CreateInstanceTest", "0.0.0.0", "00240000048000009400000006020000002400005253413100040000010001000FA0D49898864D6AFDF5C69317CBAD9E02D1BB5E514AA7BE2B981DC68CF68E7501A763BD7FA33FFE0166ED7817A903CE158463313D29F52F3DA0CD4C48E1ECF034DF64A15173E9CA16EDA95A6244C09D44BD663B72CC45337D010B2BB9AE0C39738A84F42391AC19AA35F64A44D9ED742BDB44489D7E5C6D4E866C3EA46EE6BE");

where FullTrustPolicyRemover looks like this:

public class FullTrustPolicyRemover
{
    internal void RemoveAssembly(string name, string version, string strongNamePublicKey)
    {
        var membershipCondition = new StrongNameMembershipCondition(new StrongNamePublicKeyBlob(HexStringToBytes(strongNamePublicKey)), name, new Version(version));
        var levelEnumerator = SecurityManager.PolicyHierarchy();
        while (levelEnumerator.MoveNext())
        {
            this.RemoveAssembly(membershipCondition, (PolicyLevel)levelEnumerator.Current);
        }
    }

    private void RemoveAssembly(StrongNameMembershipCondition membershipCondition, PolicyLevel policyLevel)
    {
        if (policyLevel.FullTrustAssemblies.Cast<StrongNameMembershipCondition>().Any(c => c.Equals(membershipCondition)))
        {
            policyLevel.RemoveFullTrustAssembly(membershipCondition);
            SecurityManager.SavePolicyLevel(policyLevel);
        }
    }

    private static byte[] HexStringToBytes(string hexString)
    {
        var result = new byte[hexString.Length / 2];
        for (int i = 0; i < result.Length; i++)
        {
            result[i] = byte.Parse(hexString.Substring(i * 2, 2), NumberStyles.HexNumber, CultureInfo.InvariantCulture);
        }

        return result;
    }
}