An Osaka tattoo artist was found guilty Wednesday of violating the Medical Practitioners' Law in a case that drew international attention to Japan's tattoo culture.

Osaka District Court Judge Takaaki Nagase ruled that tattoo artist Taiki Masuda, based in Suita, Osaka Prefecture, had violated the law when he drew tattoos on three individuals in 2014 and 2015, because the use of a tattoo needle was a form of medical work and not, as Masuda had insisted, a form of art and self-expression.

"With tattoo treatment, medical knowledge and skills are indispensable in order to sufficiently understand the dangers and carry out sufficient judgments and measures," the ruling said. "Therefore, unless carried out by a doctor, there is a danger to health and no guarantee of sanitation, making this a medical activity."