The United States has recently joined a growing list of several dozen nations that have prosecuted former heads of state or government on federal criminal charges in the past two decades. While Mr. Trump’s supporters claim it as the work of a “banana republic,” such charges have occurred in countries that are considered among the world’s freest, most democratic and wealthiest. Leaders in France, South Korea, Italy, Brazil, Pakistan, Argentina, Peru, South Africa, and Taiwan, among others, have all been prosecuted for corruption and found guilty. Both authoritarian and democratic leaders have historically repressed their opponents without much concern for even the appearance of due process. In recent years however, dozens of such governments have used courts, with verdicts preordained, to publicly condemn their ousted adversaries and frighten others into submission. In democracies, the evenhanded application of the law can be painted as political retribution, and vice versa, putting added pressure on prosecutors deciding whether to proceed. Legal experts point to ample ethical gray areas. A prosecution can center on what may be a real crime, yet still be politically motivated or be open to question. Despite these challenges, the justice system cannot abstain from taking on legitimate cases against political leaders.