The Washington state legislature voted to ban the use of "inflatable tube displays, persons in costume, or wearing, holding, or spinning a sign with a marijuana-related commercial message" by retail businesses selling cannabis products. On April 20, of all days.

The omnibus marijuana bill, SB 5131, has some good provisions as well: Washington residents would be allowed to share marijuana with other legal adults for the first time, and cannabis retailers would be able to operate five dispensaries (right now they are limited to three). But those liberalizations come at a cost to commercial speech.

The stated purpose behind this prohibition of pot-promoting blow-up ads is to protect children. Washington's legalization initiative—passed by voters in 2012—set the legal age for cannabis consumption at 21. And current regulations already prohibit marijuana advertisements from using cartoon characters, toys or other depictions deemed "especially appealing to children or other persons under legal age to consume marijuana."

But this apparently did not go far enough for Washington state legislators, who felt that a number of outdoor advertisements from recreational dispensaries were flouting the spirit, if not the letter of the law.

Particularly scandalous was a billboard put up by Tacoma dispensary Clear Choice Cannabis featuring a cat wearing a "thug life" collar along with text saying "I'm so high right meow." Images of that billboard—which has since been voluntarily taken down by business owner—circulated around the Washington legislature as proof of cannabusinesses potentially targeting children.

Said state Rep. Christine Kilduff (D–University Place): "When you have those big billboards out there for our youth to see, it just telegraphs legitimacy."

An amendment banning billboards was initially proposed, but this was later dialed back over First Amendment concerns. Instead signs will be limited to displaying only the name, location, logo, and type of business being advertised. Which should still raise First Amendment concerns, but apparently doesn't.

Unusual restrictions on cannabusinesses' advertising for the purpose of keeping the stuff out of the hands of children are not limited to Washington state. Colorado bans marijuana ads in radio, TV, and print unless the advertiser can produce reliable evidence that no more than 30 percent of the audience is under 21. And in Oregon the strain name "girl scout cookie" can't be displayed on packaging because it is named after a product sold both to and by children.

SB 5131 is currently waiting on the governor's signature before it becomes law.