(Jenny Starrs/The Washington Post)

AMERICA’S HISTORY of orderly freedom reflects the strength of our Constitution and laws. Yet it also demonstrates the power of unwritten rules — norms of civility and decency — that are often hard to define but always crucial to respect, lest social trust disappear and instability spread. As Judge Learned Hand famously remarked: “Liberty lies in the hearts of men and women; when it dies there, no constitution, no law, no court can save it; no constitution, no law, no court can even do much to help it.”

Unwritten rules lie at the heart of the conflict over President Trump’s firing of the acting attorney general, Sally Yates, a caretaker left over from the Obama administration. Ms. Yates felt she was honoring a vital unwritten rule — the Justice Department’s political independence — by refusing to defend the president’s executive order restricting refugees and others from seven majority-Muslim countries. Ms. Yates was absolutely right that Mr. Trump’s order is neither wise nor just, as she said in a letter made public Monday. Less certain is that the appropriate response was to remain at her post, blocking legal defenses of the order — “unless and until I become convinced that it is appropriate” to change course, as she also wrote.

The order’s legality, or lack thereof, is an unsettled issue; much of Mr. Trump’s decree, alas, may be permissible under the wide discretion that immigration statutes grant the president. Significantly, Ms. Yates herself did not state flatly that the order was unlawful, only that she was not yet convinced of its lawfulness. Given all that, she could have resigned in protest and let Mr. Trump appoint someone who could, in good conscience, defend his policy.

Mr. Trump was, accordingly, within his rights to oust her. Characteristically, however, the new president took power he legitimately possesses on paper and abused it in practice. The White House statement announcing Ms. Yates’s firing could have expressed respectful disagreement or thanked her for her long service to the government. Instead, it hurled politicized insults — “weak on borders” — at Ms. Yates and, more shockingly, accused her of having “betrayed” her department.

Among the unwritten rules that make democracy possible, none is more important than resisting the impulse to demonize political opponents. The fledgling Trump administration, like the Trump campaign before it, has violated this norm with zest. Before the White House’s ugly response to Ms. Yates, press secretary Sean Spicer told dissenters within the Foreign Service that “they should either get with the program or they can go.” Such rhetoric is having its predictable radicalizing effect on Democrats, including over-the-top tactics such as Tuesday’s boycott of Senate committee meetings on the confirmation of Mr. Trump’s Cabinet picks.

Hand gave his “Spirit of Liberty” address in 1944, before administering the oath of citizenship to immigrants assembled in Manhattan’s Central Park. In a world at war, these new Americans heard his words and looked forward to new lives in a stable political community — flawed by deep social ills but blessed by democratic processes for addressing them.

Every participant in politics today could benefit from reflecting on Hand’s message — Mr. Trump most of all.