If you belong to a club you cannot become a member of another club without doing something yourself, and that is clicking on the "quit country club" button on your club's entry page. Anyone who says poaching for members is a crime fails to understand free choice and advertising in today's world. We are all targets of advertising, whether it be to buy something, vote for something, or join a country club. And we all know that there are scams and phishing involving just about everything including "fake" news by the "fake" media.
Members who push the "quit country club" button just made a free choice and did not get poached! Perhaps they listened to the advertising or perhaps they found your club restrictive in some way. But they made the choice that was theirs and not the "new" club's owner.
Don't know what to say to those people who are not club members and then find themselves as members of a club. Generally you have to say "yes" to an invitation and if something else is happening then it is time to push that "quit country club" button yourself.