DC Sieber informed me that the because the vehicle with Modified Mufflers had been ticketed, and beat the ticket in court, it means that the vehicle was deemed "street-legal". He will therefore not pursue my Noise Complaints regarding said vehicle.
5 Illinois Compiled Statutes 140
The Illinois Freedom of Information Act, enacted in 1989 and recently updated in 2010, is a series of laws designed to guarantee that the public has access to public records of government bodies at all levels in Illinois. The updates effective in 2012 greatly strengthened the act. The law requires each public agency to nominate an officer to be the official keeper of public records, as well as complete an online training course, established by the attorney general. The act defines public records as all records, reports, forms, writings, letters, memoranda, books, papers, maps, photographs, microfilms, cards, tapes, recordings, electronic data processing records, recorded information and all other documentary materials under the control of any public body.
Anyone can request public documents but the Illinois Freedom of Information Act is not supposed to be used to further a commercial enterprise, violate individual privacy, or disrupt the day-to-day working of the public body. Government agencies must either comply with or deny a written request for public records within five working days after receiving it.
