The Swiss Federal Constitution declares the cantons to be sovereign to the extent their sovereignty is not limited by federal law. The cantons also retain all powers and competencies not delegated to the Confederation by the Constitution. Most significantly, the cantons are responsible for healthcare, welfare, law enforcement and public education; they also retain the power of taxation. The cantonal constitutions determine the degree of autonomy accorded to the municipalities, which varies but almost always includes the power to levy taxes and pass municipal laws. The sizes of the cantons vary from 37 km² to 7,105 km²; the populations vary from 15,471 to 1,244,400.