In CIS 5: Navigate to Defense+>>>Computer Security Policy>>>Defence+ rules and remove that particular application/process you Allowed or Denied. You can also Edit to Block the application, etc.
In CIS 4: Navigate to Defense+>>>Advanced>>>Computer Security Policy and remove that particular application/process you Allowed or Denied. You can also Edit to Block the application, etc.
Cheers,
Josh
[Updated by Mouse to reflect CIS 5.12.xx 19 March 2013]