Patented in the USA on September 5, 1996. Yep. That's right. Supposedly someone owns the process of putting tattoos on people to identify them.

Probably something that will never happen due to some peoples' religious objections, and due to other peoples' privacy objections. And it's just a bad idea. Besides, retina scanners and fingerprint scanners work just as well and are available now. And implanted microchips would also work better.