During the 60's and 70's the Chicago Outfit was THE number one target of the federal government and so the top bosses were already satisfied with the income which they received from different rackets, meaning they didnt need to be involved in the dope trade which at the time was Sislowly becoming THE number one illegal racket, again in the eyes of law.
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For decades, drugs were a profitable, but not huge, sideline for Mafia families. And, as long as the traffic was confined to ghetto areas, minorities, musicians and others society didn't care about, drugs only sporadically appeared on law enforcement/political radar. The explosion of drug use in the sixties and seventies ruined the lives of many young white kids--including sons and daughters of police, judges and politicians. Enforcement was stepped up, and sentences for trafficking moved well into the double digits. NY's "Rockefeller Law," which decrees life in prison with no parole for just
possession of salable quantities of hard drugs is still on the books.