In Canada, driving under the influence (DUI) is defined as having a blood alcohol level exceeding 80 mg per 100 ml, with penalties escalating based on the number of offenses. First-time offenders face a $1000 fine and a one-year driving prohibition, while repeat offenses lead to increased jail time and longer prohibitions. New DUI laws impose stricter penalties and give police greater authority to assess impairment, emphasizing the importance of consulting a specialized DUI defense lawyer.