Since the late 1970’s, Canadian authorities have introduced three gun control laws, namely Bill C-51 (1977), Bill C-17 (1991) and Bill C-68 (1995). Currently, the preventive effect of these laws on homicides is highly controversial. Although several studies have been conducted to date, the latest contain numerous methodological flaws that threaten the validity of their results. While overcoming the limitations of previous evaluations, the objective of this article is to assess the effect of Bill C-68 on homicides in Quebec, Canada, between 1974 and 2006. Results from our extreme bounds analysis (EBA) reveal that Bill C-68 is associated with a gradual decrease in firearms-related homicide ; no substitution effect is observed. This gradual decline is observed, however, exclusively in homicides committed with long guns (rifles and shotguns). Further studies are needed to pinpoint the specific effects of licensing and gun registration on homicides.