Given the recent calls by several Latin American presidents for a debate on legalising drugs, would the United States show any flexibility in its stance on prohibition? “None,” was the answer of Joe Biden, America’s vice-president, who was in Mexico City on March 5th to meet the three main contenders in July’s presidential race. Mr Biden arrived under unprecedented pressure from regional presidents for the United States to give way on prohibition, which many in the region blame for generating appalling violence.