The US is currently facing a government shutdown because Donald Trump is insisting any spending bill must fund the construction of a US-Mexico border wall, which would cost as much as $18 billion. Bound up in symbolism about the racial purity of the United States, the wall has been sold as a way to prevent both illegal immigration and the trafficking of drugs over the southern border. But the actual solution to securing the border against drug smuggling may be simpler and cheaper than Trump realizes: Rather than stop the flow, why not just grow the drugs here?