How to lock down objects like stored procedures without using object level permissions (SQL 2008)

There is a way to lock down stored procedures so that it is impossible to modify them even if you have system administrator priviledges.

As a new person in a particular company I was given the sa password but later found out I could not modify the stored procedures because all stored procedures had that option dimmed out.  If you right clicked on the sp, the pop up menu displayed the 'Modify' option but it was dimmed out.

Thus, how could it be possible to have such an option dimmed out to a system administrator?

Thanks