Good News ....Weed is legal in IllinoisWeed is legal in Illinois Pot smokers in the Midwest, rejoice. Anyone 21 and older can buy and possess recreational marijuana in Illinoisbeginning in the new year. Illinois becomes the 11th state to legalize recreational marijuana Illinois becomes the 11th state to legalize recreational marijuana Under the law, Illinois residents will be able to purchase and possess 30 grams of cannabis, five grams of cannabis concentrate and cannbis-infused products containing no more than 500 milligrams of THC. People who don't live in Illinois can buy half of each of those amounts. Medical patients can buy marijuana seeds and grow up to five plants at home, as long as the plants are kept out of public view. The law also pardons individuals with nonviolent convictions for amounts of cannabis up to 30 grams.