Portugal's case is important, Greenwald says, because it provides hard evidence that removes the debate from the realm of speculation.
"If you're the first state to do it, there's really no way you can point to evidence of what will or will not happen. … It's just theory and it's very abstract," he said. "The more examples that arise and the more that you can prove that the sky doesn't fall in," he said, the more politically feasible drug liberalization will become in the U.S.
So far, Portugal has largely flown under the radar, even in drug policy circles. But Greenwald says that, six months after his paper was released, he's getting more invitations than ever to present it. In August, New York Times columnist Nick Kristof cited it in a column praising Webb's reform push.