Upon assuming the presidency, many observers expressed reservations about what a Trump administration foreign policy would look like. More than any other representative of President Donald Trump’s government, United Nations Ambassador Nikki Haley has answered those critics. At the UN, Haley has articulated a clear vision of how America would handle itself on the world stage: a stalwart friend to its allies, fearsome foe to its enemies, and consistent voice of reason in a forum often governed by the whims of authoritarian regimes and violent special interests. This week, for example, Haley made clear the Trump administration would stop at...