Is there a way to ensure all members have to re-accept the policy when they next sign in?

As soon and you change the version of your TC, the system will notice that and will force new logins to re-confirm the T&C. So much for the technical part. It would be good to send out comms and tell them in a nutshell what has changed and what that means for them.

This is however site wide. Group wide you can send them a mail provided they have a unique system role and tell them that the rules of the game have changed a bit.

Thank you!

Wilfried Rijsemus (3sides) said:

As soon and you change the version of your TC, the system will notice that and will force new logins to re-confirm the T&C.

A small note here - I've been testing this functionality, and, in my experience, it applies to the next page load of any user who's currently logged in, not just the next time someone logs in. 

:-) Alex Nassi for president!

Thanks for clarifying Alex