1 general:: Phrase(s): opt out (of something) to choose not to be in something. • If you do that, I’m going to have to opt out of the club. • Then go ahead and opt out.
McGrawhill's American Idioms And Phrasal Verbs
2 general:: Choose not to participate, as in Our school opted out of the state competition. [Slang; mid-1900s]
American Heritage Idioms