(Pro 28:4 KJV) They that forsake the law praise the wicked: but such as keep the law contend with them.
For some clubs you don’t need a membership card to participate in activities. Your participation in the activities is all the ID you need. The real requirement is an attitude that produces certain behaviors. If you are a thug in a parking lot looking for someone to rob, you watch behavior and ask yourself who is acting in such a way as to be an easy victim. If you are bar hopping and looking for a temporary companion, you know what to look for. It isn’t the lady crossing the street so she doesn’t have to walk by the entrance.
Can you tell who is a Christian by behavior? In many cases, no. You can fake it. Can you make some clear decisions based on behavior? Yes. When someone introduces me to a same sex partner who they call their spouse, I know there is almost no chance they are Christians. I say “almost” because it is possible that they are new believers and have not dealt with the sin in their lives yet.
So? Make sure you are on the team you claim. It is embarrassing to show up at the club house and find out they have re-keyed the locks.