I clicked on the database name, Security tree, Users, right click his Username, Properties, Securables on SSMS2008. There is nothing on the Permissions: Explicit.
When I run
USE [dbname]
GO
EXEC sp_helpprotect NULL, 'john'
I get
Msg 15330, Level 11, State 1, Procedure sp_helprotect, Line 346
There are no matching rows on which to report.