This question does not make sense. The poster seems not familiar with SQL Server. If a database instance runs under a client machine, any Windows administrator can certainly log on the SQL Server instance even without using detach/attach methods and your SQL account password. SQL Server has two authentication modes: one is Windows Authentication; the other is Mixed Authentication mode. So any Windows administrator of the client can log on the instance and manage the database.
Since the SQL Server was installed on a client machine, it is impossible to block the client administrator to manage the database. I have to say that no resolution can prevent a client administrator to administrate his machine and SQL Server instances.