Another problem with having laws against certain types of plants is that police don't know anything about plants. The subtleties of botany are inevitably lost on them and the results are amusing, yet tragic:

THE HAGUE, Netherlands — Dutch police who mowed down what they thought were illicit marijuana plants were red-faced today when it emerged they’d ruined a research group’s giant, officially sanctioned field of harmless hemp.Police proudly announced Wednesday that they’d found more than 47,000 cannabis plants, with an estimated street value of nearly €4.5 million ($6.45 million) concealed in a corn field in the Flevoland province east of Amsterdam.They mowed down half the plants only to be informed they were the property of Wageningen University and Research Center, a respected agricultural school. [Boston Herald]

That sucks. Sadly, I suspect that the potential for fiascos like this goes a long way towards explaining why law enforcement continues to incoherently oppose hemp cultivation here in the U.S. Police just don't want to be bothered with distinguishing one from the other. If it looks like weed, they'd rather break out a machete than a field manual. It's understandable if you don’t care about, like, freedom and stuff.

Instead of banning hemp, therefore, I propose we just legalize all forms of cannabis and make things a lot easier for everyone.