CC licenses function within copyright (the “all rights reserved” approach), yet they differ by employing a “some rights reserved” approach. By default, all CC licenses grant the public permission to use the works. The licenses provide for additional conditions, but remain in place for as long as the underlying copyright lasts or until a reuser violates the license terms. It is fundamental to clarify that CC licenses work on top of copyright, not instead of copyright.
Welcome to yet another post in the #CCByBrian series.
CC licenses are standardized – which means the terms and conditions are the same for all works subject to the same type of CC license. Despite creatives and authors who use the licenses wanting to make modifications to meet diverse ( or slightly different) needs and wants, CC strongly discourages from customizing open copyright licenses. Aside from the confusion this might create, it will take an immense amount of time and effort for users to learn about these bespoke customization. If you change any of the terms and conditions of a CC license, you cannot call it a Creative Commons license or otherwise use the CC trademarks. This rule also applies if you try to add restrictions on what people can do with CC licensed work through your separate agreements, such as website terms of service or privacy policies.
There is a detailed CC legal policy outlining these rules, but the best way to apply them is to ask yourself: is what you want to do going to make it easier or harder for people to use your CC licensed work? Note that all of the above applies to creators of CC licensed work. You can never change the legal terms that apply to someone else’s CC licensed work.