Restrict Users from Creating Community Groups

  1. Go to Communities > Select Groups > Click Groups > Click Group Settings

  2. Set "Allow Group Creation" to NO 

With Allow Group Creation Set to No, no users will be able to create Community Groups.

Or, set "Allow Group Creation" to YES and "Moderate Group Creation" to YES to allow users to create user groups, upon moderator approval.

If Moderate Group Creation is set to Yes, Users will be able to create community groups pending moderator approval.
If Moderate Group Creation is set to No, Users will be able to create community groups without moderator approval.