A bill that could impose taxes on all illegal drugs was approved in a Missouri house committee on Thursday, which, if passed, would make Missouri the 21st state to collect taxes on illegal drugs.

According to the proposed law, those in possession of drugs—any illegal drug from marijuana to heroin and methamphetamine—would be required to buy a state-issued tax stamp, which could be purchased anonymously ahead of time. Any individual caught with illegal drugs who does not have a stamp could face a fine or additional criminal charges.

Currently, 20 U.S. states already require those who possess illegal drugs to purchase state-issued stamps for his or her contraband, according to the National Organization for the Reform of Marijuana Laws (NORML). However, few citizens observe these laws because they are either unaware that such laws exist in their state or they fear that complying will incriminate their behavior.

Revenue generated by the drug tax stamps would help fund law enforcement and drug treatment programs, according to the bill’s sponsor Rep. Shawn Rhoads (R-West Plains).

But critics of the drug tax bill, like Kansas City democratic Sen. Jason Holsman, call it “an attempt to self-fund the War on Drugs,” and that despite being able to purchase drug tax stamps anonymously, it could still represent a violation of the constitutional protection against self-incrimination.