You cannot remove a policy from a group(s) or user(s). What you can do instead is reapply the Global policy to the groups or users in question by setting up a Rule and including the groups and users you wish to set the Global policy and set the Policies to Global in that Rule. This will reset the policy to your global policy settings.
IMPORTANT: The placement of the rule will depend on the other rules you have in place. Keep in mind the order does matter and it goes from Top to Bottom where the top is the most granular and the bottom being more broad (global).