President Donald Trump has been criticized for breaking numerous political norms during his two presidencies, including, for example, the norm against launching criminal investigations of political opponents. The idea is that even when a president doesn’t violate the law, he or she is (or should be) bound by important political norms that ensure that democracy functions. But what does it mean to say that a political norm exists? During his lecture, Eric Posner (Professor of Law at the University of Chicago) considers two theories: norms reflect fundamental political commitments, akin to constitutional restrictions; and norms are merely endogenous to regular political behavior, including the value of cooperating across political lines. Both theories raise questions about the value and importance of political norms.