Colin P. A. Jones discusses the often arbitrary way that Japanese laws are enforced.
Foreign visitors to Japan often comment on how polite the Japanese people are, but little do they know that it is actually against the law to be rude. Under Article 231 of the Penal Code it is a crime to “insult another person in public.” It would be tempting to dismiss this as a quaint remnant of the Code’s Meiji roots (it was enacted in 1907 and written in classical Japanese until 1995). However, several years ago a man was arrested for calling a woman “fat” in a bar. He was also detained for 29 days for this infraction. Given that Japan’s Supreme Court has recently held that liability for criminal defamation may arise from anything posted on the Internet, Japanese people could conceivably soon become famous for being polite online too.
Prosecutorial discretion exists in other countries too (and is often abused) but Japan takes it farther than most.