Sounds nuts at first but actually it's brilliant. It's a clever legal stroke. They know that no drug dealer will buy stamps. You'd have to be on drugs to do that. But when you are caught with untaxed drugs you lose everything, house car and the shirt off your back. This being the crucial phrase.
* Laws exempting personal property from seizure do not apply to seizure pursuant to drug tax warrants.
Very clever indeed. Here in Ireland we have the CAB, Criminal Assets Bureau. They do much the same thing very successfully. A lot of gangsters have lost most of their property that way.