Typically there'll be a CMS flag available to powerful users (editors). That's how it works at the Guardian.

It sets a boolean (shouldHideAdverts) in our content API[0], which we use in templates[1] to suppress commercial logic.

There are obvious business reasons for this. It's common for it not to be in the advertiser or reader's interest to show commercial messages against some content.

[0] http://content.guardianapis.com/world/live/2015/mar/24/germa...

[1] https://github.com/guardian/frontend/blob/4cb7e07c15a03568c2...