Of course, if you want to have such a tax, you must make sure that there's a wall between revenue agents and the drug police (or the tax would likely be unconstitutional under the 5th Amendment). A lower court found that Tennessee's tax violated that.
However, the Tennessee Court of Appeals ruled that the tax also violates the Tennessee Constitution, in that "...the statute is arbitrary, capricious, and unreasonable and, therefore, invalid under the Tennessee Constitution, in that it seeks to tax as a privilege, activity that prior legislation has designated as criminal activity...."
Tennessee will appeal to the Tennessee Supreme Court.
News Story: The Tennessean
Hat Tip: Tax Foundation