The four journalists from Sansai Books were responsible for a magazine issue that provided details on DVD ripping, and included with the cover-disc were some of the freely available DVD ripping tools. But under the, perhaps ironically named, Unfair Competition Prevention Act (UCPA), doing any of this became a criminal act, and so the police had to intervene after warnings were issued to the publisher to stop selling the magazine.
It is unknown at this time why Sansai Books was targeted, as many other competitors produce similar magazines, and dozens are still available for sale on websites such as Amazon Japan. Otaku News
, the blog that first broke the news, theorizes that authorities may be keen to make an example out of Sansai Books as a warning to others.
Under recent changes to Japanese copyright law, anyone caught watching pirated videos on websites such as YouTube could face up to 2 years in prison. Personal backups of DVDs were also criminalized as part of the changes.
These changes have also caused collateral damage to other parts of the tech sector. Linux distributions are now mostly illegal in Japan due to the fact that most include the libdvdcss library used to offer DVD playback support, but the same library can also be used to remove copy protection code on DVDs.