This article analyzes how the law against blasphemy has become a weapon against religious minorities in Pakistan. It begins with a brief overview of the constitutional struggle between the forces for religious tolerance and that element of Pakistani society seeking a particularized Islamization of Pakistan's law and culture. The second section of the article explains the manner in which classical Islamic law (the Shari'a) treated apostasy and blasphemy, and how it permitted private acts of religious vengeance to be immune from legal liability. In the final section, I describe how the current law on blasphemy imposes a harsh regime on religious minorities, allows private acts of vengeance to go unpunished and mimics the classical prohibition against apostasy to work against dissenting Muslims as well.