It is not really covered in the laws but you are not exposing anything so it would be no different than a bikini. Therefore have fun showing off your diaper.
A diaper is nothing more than a type of underwear so if it is under your clothes I don't see what the problem is. Many adults with bowel or bladder control problems wear diapers or pads in public. No one has to know. And no it is certainly not illegal.
Been a baby
Not any more then wearing underwear. If your running around in nothing but a diaper, you will probably be cited for disturbing the peace or child abuse (if it's sexual and children are around). However, if you wearing them under clothing, then no.
This probably would not be allowed. You would be arrested for public indecency. Not to mention "no shoes, no shirt, no service" at McDonalds.
if you mean is it illegal to then no , it is not illegal to wear a hazmat suit in public but you may get in trouble for consealing your face on private property.
No, it is not illegal to wear a Guy Fawkes mask in public in the state of Maryland in the USA.
Let him wear a diaper.
Sure. They fit pretty well under your clothing.
the best way is to wear baggy clothes and wear a small diaper
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yes
Turn into a baby diaper?! No that's silly. Turn into a baby? That's just as silly. If you need to wear a baby diaper, then you need to wear a baby diaper. If you want to wear a baby diaper, go for it if it fits. Maybe you should think about adult diapers, then you might turn into an adult (lol).