The conflict between the European Union and Poland’s right-wing government went up a notch on Wednesday when the European Parliament passed a resolution calling on Poland’s rulers to stop defying the country’s top court.

Unfortunately, the resolution is not likely to sway Jaroslaw Kaczynski and his fellow nationalists in the ruling Law and Justice Party, who believe that it is their mission to zealously defend socially conservative Catholic values and Polish sovereignty against a secular E.U. and a multiethnic Europe — even if that means trampling on the rule of law.

Poland’s government and its top court, called the Constitutional Tribunal, locked horns after Law and Justice came to power in national elections in October and, to ensure that the court could not block the government’s right-wing agenda, began trying to reduce the court’s powers by naming several new judges and then passing a law that would change the way the court functioned.

The court ruled that only three of the proposed judges could be legitimately seated and that the legislation was unconstitutional. The government refused to recognize the ruling, setting off a constitutional crisis. Since then, the European Commission and the Council of Europe, the continent’s human rights organization, have assailed the government’s actions and have demanded that Poland abide by the court’s ruling.

The dispute between Warsaw and Brussels is an illustration of the culture gap within the E.U. Many of the union’s new Eastern and Central European members chafe at the sense that they are being treated as second-class members. Reacting to the European Parliament’s scolding, Prime Minister Beata Szydlo charged that Western European politicians feel superior to new members and “like to instruct others.”

In fact, there is little the union can do to compel Poland or any other member to alter its conduct, even though the resolution passed by a vote of 513 to 142. The resolution is nonbinding, and any punitive measures would require unanimous support in the European Commission, the union’s executive arm. Hungary’s similarly nationalist government, for one, would not support any such measures. Too much overt pressure, moreover, would only harden Mr. Kaczynski’s resentment of the union.

Yet it is incumbent on the European Union — and on the United States, which the Poles rightly see as their close ally and protector against Russia — to make clear to the Polish government that the rule of law is not a take-it-or-leave-it imposition by the “old E.U.,” but a central tenet of the democracy Poland signed on to.

As Poland prepares to host a NATO summit meeting in July in the hope of landing large contingents of allied forces on its soil, Washington should remind Mr. Kaczynski that the alliance is, above all, one of shared values.