A new law in which came into force today in Japan threatens web users who illegally download music with up to two years in jail.
The law was approved in June, but came into force today.
The Japanese government has already faced protests from web users wearing the trademark Guy Fawkes masks affiliated with the Anonymous movement.
Protestors claim that the new law allows for widespread surveillance of ordinary internet users.
It has also aroused concerns from copyright campaigners - most such laws only permit fines for illegal file-sharing, rather than jail terms, and many countries only target users who upload music, rather than download it.
Under the new law, people who download music face up to two years in jail or fines of up to two million yen (£16,000).
Users who have downloaded a single MP3 song could in theory be charged.
The Recording Industry Association of Japan claims that illegal downloads in Japan outnumber legal purchases 10 to 1.
The data comes from a 2010 study of music in Japan, where users downloaded 440 million tracks legally, and 4.4 billion illegally.
The legislation was described as 'One of the most draconian in the world' by file-sharing site Torrentfreak.
Uploaders already face up to 10 years in prison and a 10 million yen (£80,000) fine.