How to implement privilage based security in web api?

Hi All,
           I have requirement where i have some users, roles, privileges to access resources. I need to implement privilege based security for web api, if user passes some means of credentials to access some resource on the web api, web api need to validate the request depending on that user privileges. If user having privilege to access the resource then controller action should perform otherwise it should return the error message.I have found token based authentication scenarios on the web, if any body come across this type of security. Please post your methodology in achieving this.