Cavallari has a California license, but Illinois law requires people who have lived in the state for 90 days to have an Illinois license.
The 26-year-old, best known for her role on MTV reality television show "The Hills," was stopped around 11:50 a.m. heading north on Sheridan Rd. near the Evanston/Chicago border.
Since her license was from California, which does not participate in a reciprocal agreement among states regarding licensing, she was escorted to the Evanston Police Station to post $150 bond.
After the incident, Cavallari took to Twitter, claiming she is still a resident of California.
She reportedly received a $120 citation and is not able to drive until she gets a valid license in Illinois.