If a service member was given a direct order not to smoke spice and did so, the service member can be charged with violation of UCMJ Article 92, violation of a direct order. A service member can be given an Article 15 punishment, or a Court martial. A court martial could be discharged from the military as a result of the Court martial.
Whether or not something is sold in a store doesn't mean its legal for service members to use. Remember, marijuana is legal in California with a physician's recommendation, and it is sold in stores.
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