Only let user navigate to specific page in frontend on condition?

I have a custom module in which the user should only be able to navigate to a page in the frontend when the “Demo mode” setting is set to true in the configuration of the module. I am able to get the current state of the setting in the frontend, but don’t know how to go about enabling/disabling navigating to a specific page. Essentially when the setting “Demo mode” is turned of, the user shouldn’t even be able to open the page.