Objective: The objectives of the study were to describe the distribution of tetrahydrocannabinol (THC)-influenced drivers in a new Danish 3-level offense system and discuss the consequences of the changed legislation. Methods: By request of the police, blood of individuals suspected of driving under the influence of drugs (DUID) in Funen and Southern Jutland was sampled by medical staff and shipped to the Section of Forensic Toxicology of the University of Southern Denmark in Odense. Samples from individuals suspected for driving under the influence of cannabis (DUIC) were stored at 5 °C prior to immediate analysis, and THC content in whole-blood samples was established by gas chromatography–mass spectrometry analysis. Quantitative results for blood THC levels were available from 2017 and 2018, resulting in 2,206 eligible cases. Data before and after the legal change on December 15, 2017, were extracted from the department’s laboratory information management system. Results: With the new graduated sanctions introduced in December 2017, 70% of the DUIC suspects faced milder sanctions. The number of DUIC cases has been increasing and has almost doubled in the last 4 years, from 648 cases in 2015 to 1,206 in 2018. Correspondingly, the total number of DUID cases increased by 80% from 898 cases in 2015 to 1,614 cases in 2018. The concentration of THC in blood was above the legal limit of 0.001 mg/kg in 73% of the cases; 18% had concentrations categorized as low, 32% as medium, and 22% as high. Conclusion: We found that more than two-thirds of the THC offenders faced milder sanctions compared to before the new legislation, suggesting that the new graduated legislation has had a significant impact. The current trend is a steadily increasing number of DUID cases. We believe that the continual increase is caused by a combination of factors, including increased police awareness and training of police personnel along with improved roadside screening abilities.