Retired doctors "can and want to help those in need, and we should let them," Quinn said in a statement. "It's just common sense to broaden access to health care, which is a fundamental right as a human being."
The legislation allows retired health professionals, including dentists, physician assistants and optometrists, to get credentials so they can continue working as volunteers. It waives fees for the first 500 volunteer licenses. Holding a regular license and a volunteer license at the same time is prohibited.
Dentists will be able to give flu vaccines to patients ages 18 and older who have a prescription or a doctor's order, under a separate law enacted Saturday.
Quinn also signed legislation directing the Illinois Department of Public Health to set rules and regulations regarding food sampling and testing at farmers' markets.
"This new law will encourage people across Illinois to get out and buy local," Quinn said.