ON A street corner five blocks from Congress, a transaction of uncertain legality is taking place. A man in his 20s, wearing a red Stanford University hooded top, is handing your correspondent a bottle of fruit juice. The cost? $55. The juice’s steep price does not reflect yet another innovation in artisanal pulping. Rather, it explains the free gift that accompanies the juice—a branded green bag containing about an eighth of an ounce (3.5 grams) of cannabis.

Since 2015 it has been legal to own, grow and use cannabis privately in Washington, DC. Generous souls are allowed to give small amounts to whomever they like. It is illegal, however, to sell it. Small businesses have sprung up seeking to exploit this dichotomy. With names such as HighSpeed, Kush Gods and 24/7 Strong Supply, their main objective is clear. The most notorious business, Kush Gods, sends cars emblazoned with cannabis leaves around the city to solicit “donations” from passers-by in return for cannabis-infused edibles or pre-rolled joints. The four states that have legalised cannabis for recreational use have also set up systems to tax and regulate it. In DC, which has not, something like a barter economy has sprung up instead.

Unusual though this may be, it arises from a familiar political tussle between the federal government and the place it calls home. The city is a federal jurisdiction; its budget must be approved by the congressmen who sit on Capitol Hill, some of whom are not keen on creeping marijuana legalisation. Shortly after the legalisation ballot was passed, a congressional rider was attached to DC’s budget forbidding the use of federal or local funds for regulating the market.