Check it out. It's a quick read -
http://reesenews.org/2011/09/16/tax-on-roll-your-own-tobacco-has-smokers-regulators-conflicted/19636/
http://reesenews.org/2011/09/16/tax-on-roll-your-own-tobacco-has-smokers-regulators-conflicted/19636/
If the intent of the tax is to discourage cigarette smoking, and the difficulty in distinguishing RYO tobacco from pipe tobacco is insuperable, then tax rolling papers and RYO paraphernalia, and allow the industry serving thousands of epicurean pipe smokers to thrive.