In his attacks on law firms, universities and other American institutions, President Trump is relying on an illusion. The illusion is that the institutions are powerless to fight back and that they face a choice between principle and survival.

These institutions do not have to capitulate to Mr. Trump. They have a realistic path to defeating his intimidation. Some law firms and others have begun to fight. In doing so, they have provided the beginnings of a playbook for standing up to his…