The City of Chicago regulates the retail sale of alcohol. The Illinois drinking age is 21.Under this guideline, it is illegal for anyone under the age of 21 to purchase or try to purchase an alcoholic beverage. Chicago statute 8-4-030 states that it is unlawful for any person to drink any alcoholic liquor in public or in a motor vehicle upon a public way in the city. The City of Chicago does not regulate the practice of BYOB. Our Illinois liquor license attorneys assist with local, state, and federal applications for manufacturers, distributors, and retailers. If you're charged with alcohol related crimes in Illinois, contact a Chicago criminal defense lawyer with O'Meara Law at (312) 428-4000 for a free consult. Randolph Street Suite 7-801, Chicago, Illinois. Liquor licenses are issued annually effective May 1 to April 30 of each year. The legal limit in Illinois for blood alcohol purposes is 0.08 grams of alcohol per 100 milliliters of blood.