WCF operation result - wcf

Question

There are two users: ManagerOne and ManagerTwo. Before use my service they must login.
public class MyService : IMyService
{
int _userID = -1;
public bool LogIn(int userID, string password)
{
if( UserCheck(userID, password) )
_userID = userID;
else
throw new FaultException<InvalidUserFault>(new InvalidUserFault());
}
}
After login they can run GetSome() operation. This operation return some my DataContract. And this operation can run only ManagerOne. If ManagerTworun GetSome(), operation must return error. The question is: what is best practice - return OperationResult<T> or FaultException (in THIS scenario)?
See some code:
public class MyService : IMyService
{
int _userID = -1;
public bool LogIn(int userID, string password){...}
public OperationResult<SomeDataContract> GetSome()
{
if(_userID != 101)
return new OperationResult<SomeDataContract>()
{
Result = false,
ResultMessage = "User hasn't permission",
ReturnValue = null;
};
.....
}
}
Or:
public class MyService : IMyService
{
int _userID = -1;
public bool LogIn(int userID, string password){...}
public SomeDataContract GetSome()
{
if(_userID != 101)
throw new FaultException<MyFaultContract>(new MyFaultContract("User hasn't permission"));
}
}
In classic app I would use GenericResult, because I think it is not exception. But what about WCF? Is FaultException normal practice for my scenario?