I'm fond of the restriction which you can turn off, better still might be a notice that says something like "The action you have attempted to perform is forbidden by the DRM settings on this file. Okular can ignore these settings but other PDF viewers may not. Following the law is your responsibility. [Ok] [Ignore DRM flag]".
It's very useful to know that a file has restrictions, and some people may appreciate the reminder that copying from the file is unwelcome and may be a violation of the law depending on the specifics of the situation.