The following are the exceptions with regard to the above-mentioned settings:

 No Override:

Any GPO can be SET to No Override. If the No Override configuration is set to a GPO, no policy configured in the GPO can be overridden. If more than one GPO has been set to No Override, then the one that is the highest in the Active DIRECTORY hierarchy takes precedence

Block Policy INHERITANCE: 

The Block Policy Inheritance option can be applied to the site, domain, or OU. It deflects all group policy settings that reach the site, domain, or OU from the object higher in the hierarchy. However, the GPOs configured with the No Override option are always applied.

The following are the exceptions with regard to the above-mentioned settings:

 No Override:

Any GPO can be set to No Override. If the No Override configuration is set to a GPO, no policy configured in the GPO can be overridden. If more than one GPO has been set to No Override, then the one that is the highest in the Active Directory hierarchy takes precedence

Block Policy Inheritance: 

The Block Policy Inheritance option can be applied to the site, domain, or OU. It deflects all group policy settings that reach the site, domain, or OU from the object higher in the hierarchy. However, the GPOs configured with the No Override option are always applied.