As I am not a lawyer I cannot comment on who has rights to what.
From a development prospective, if there is data in your database which you do not want anyone else to ever see, then the database should not be installed on your clients' machines with MS SQL Server.
Microsoft have always been upfront about how it's product works so it is up to you, as the developer, to choose the right product.
The only database I am aware of which might provide the level of security you want on a client's machine is Oracle. This is usually a lot more expensive to license.
Most software vendors, who want to protect their intellectual property, just have confidentially clauses written into the license contract.