I remember watching a show on the history of drugs in America. Opium at the turn of the 20th century was legal in America. Sears & Roebuck also offered Heroin along with a syringe from their catalog of 1900. On the show they mentioned many soldiers who came back from the Philippine American War were addicts from the Opium dens in Manila. The entry dock from Manila to the US for these soldiers was San Francisco, where the largest Chinese community was located(China town)...and the soldiers would continue their addiction at the opium dens there.
If America at one point thought opium was harmless and didn't ban the substance, then to me there is a small possibility opium was not a illegal drug by the Moros either.
From the Sears & Roebuck catalog
