What cannot be done by the states according to the federal Constitution?

Under the federal Constitution, states are explicitly prohibited from declaring war. The power to declare war is reserved for the national government, specifically Congress, as outlined in Article I, Section 8. This centralization of the war power ensures a unified national stance on military matters, which is crucial for maintaining national security and diplomatic consistency.

The other options represent powers that states can and do exercise. For instance, states have the authority to provide education through local school districts, establish local governments to manage their own administrative tasks, and regulate intrastate commerce, which refers to trade and business activities conducted within the state's own borders. Each of these functions is a vital component of state governance and reflects the principles of federalism where states maintain significant powers alongside the federal government.