From his Illinois home, he champions guns for all. The Times confirmed his real name and linked the firearm he helped design to terrorists, drug dealers and freedom fighters in at least 15 countries.After an attempted gang murder in the French city of Marseille last year, the police found what appeared to be a toy assault rifle, seemingly crafted from plastic and Lego parts. “But the weapon was lethal,” Col. Hervé Pétry of the national gendarmerie recalled. In the past three years, this model of homemade semiautomatic firearm, known as an FGC-9, has appeared in the hands of paramilitaries in...