It’s a bullish time for executive power. President Donald Trump’s conception of it is so expansive that he has asserted that he can pardon himself. The Supreme Court has reinforced that conception by upholding Trump’s blatantly anti-Muslim executive order restricting immigration. Trump’s belief that presidential authority is practically monarchical, his belligerent posturing toward countries such as Iran and North Korea, and his cavalier disregard for legal procedure have made many observers wonder if he will try to start a catastrophic war, and what safeguards exist to constrain him if he does.