If I understand your question, it sounds like you're looking for something like Transparent Data Encryption, in hopes of preventing a user detaching the database, attaching it to their own server, making changes, and re-attaching it to the original server. Transparent Data Encryption would require the user to have a certificate and a private key in order to attach or restore the database to a different server.
This requires Enterprise (or Developer or Evaluation, neither of which is licensed for production use), and I'm not convinced it's 100% foolproof if the user has administrative access to the server. You'd need to prevent the user from having access to export the certificate, for example.
Unfortunately, joeqwerty is correct that you'll need to not give the user Administrative access to the server or SA access to SQL, and will have to block the user's NTFS permissions to the SQL directories, etc.