The Denver Post reports the Castle Rock town council approved an ordinance Tuesday that imposes a $300 fine on anyone caught selling the substance to minors. The town late last year imposed a six-month moratorium on the licensing of any new kratom shops while new rules were established.

Kratom, which is derived from the leaves of a tree that grows in southeast Asia, often is used in the form of an extract or a pill. Many see it as a safe, natural alternative to opioid painkillers. But the Food and Drug Administration says it exposes users to the risks of addiction, abuse and dependence.