Resultant Set of Policy (RSOP)
RSOP displays a list of computer and user settings. It details the Group Policies that have changed each particular setting.
Add RSOP via the MMC.
Find the particular setting you are interested in. In this example we want to find the Inbound Firewall rule for RDP. Once you have found the setting right click on it and select properties.
Click on the Precedence tab to view which particular Group Policy is affecting the setting.
Now that we have identified the GPO you can use the Group Policy Management Editor to edit it. This will allow you to change the Inbound Firewall rule for RDP. Within the editor navigate to the same location that you did within RSOP. Right click on the desired setting and select 'Edit'. You now you can directly modify the effect of the GPO.