Brazil’s new president, Jair Bolsonaro, signed a temporary decree on Tuesday fulfilling a campaign promise to tackle the country’s epidemic of violence by making it easier for Brazilians to buy guns. Bolsonaro, a conservative former Army captain, was sworn in as president on Jan. 1 after sweeping to power last year on a hard-line law-and-order platform, pledging to reduce the countrys record murder rate and booming trade in illegal drugs that fuels it.