Warner Music, EMI, Vivendi Universal and Sony BMG ‘investigator’ MediaSentry is fast becoming outlawed in many U.S. states.

The Massachusetts State police have already banned the company, it has been accused of operating without a license in Oregon, Florida, Texas and New York, and now similar charges have been leveled at it in Michigan.

Evidence gathered by the RIAA's pit bull has been a key element in getting clients to pay up. However, it is starting to look like the outfit's unauthorized snooping could get it into trouble.

State prosecutors can prosecute cases against Media Sentry as felonies, with a maximum penalty of a $5,000 fine and/or up to four years in prison.

More here.