Unfair practice

According to the reception at the gym planet fitness has introduced a rule that kids under 18 should enter with their own tags. But to my surprise 3 weeks back I was stopped to be notified that mine won't be allowed in without tags. The very same day people were passing with their kids without tagging & nobody was saying anything to them, when I asked I was told they were notified don't know when. Up to this Day I attend the gym every day kids pass without tagging. Unfortunately it's whites that have a right to do so. They pass without a problem but I was stopped and notified while they were physically not here. This is ******