So take a predator. Who has a penis they thoroughly enjoy and is also interested in children.
They sign the declaration. They go and hang out at toddler swim. Moisturising their thighs after their swim, just like any other woman, whilst glancing at all the children.
They're very friendly and chatty to the mums - your little Johnny is sweet, how old is he? Massage, smirk. Not illegal, backed up with a piece of paper. You go out to the reception and say something. What can they do? Do they suddenly say no mosturising in the changing rooms? No smiling? No talking to mothers?
If anyone questions them, they have a piece of paper in their pocket that says there are perfectly entitled to be there. Smirking and moisturising isn't a crime.