Senior officials from two founding members of the EU on Friday expressed fears that a Polish ruling challenging the supremacy of EU laws could trigger the country’s exit from the 27-nation bloc. French Secretary of State for European Affairs Clement Beaune said that Thursday’s ruling from Poland’s Constitutional Tribunal was an attack against the EU, while Luxembourg Minister of Foreign and European Affairs Jean Asselborn said Poland was “playing with fire.” They spoke a day after the tribunal ruled that Polish laws take precedence over those of the 27-nation bloc, which Poland joine...