Cannabis decriminalization measures across the United States, including the medical use of marijuana in California, have been sharply criticized by the United Nations, which has warned Washington they violate the international drug conventions. The International Narcotics Control Board (INCB), which polices the drug treaties, has also warned about the growing public health threat from the “unprecedented surge” in “legal highs” and called for concerted global action to curb the growing trade. … The INCB has warned the US government that medical cannabis must be properly regulated. “In some US states, they are being operated in a way that is completely...