can you remove/delete a group notice?

[RuiBerto]

can you remove/delete a group notice after sent even if your the group owner? if so how?

[Alwin Alcott]

no

[Pixieplumb Flanagan]

Whilst you cannot remove a notice, you can disable the ability to receive or view notices until the notice in question has expired, which I think is 2 weeks.

To do this, go to Roles, Everyone, Notices and uncheck Recieve notices and view past notices.

It's a bit extreme, but if you have inadvertently sent something your should not have, it's the only way to prevent it going to all members.  This won't affect anyone who already got the notice, of course.