What is one of the powers denied to the states by the Constitution?

The power to regulate foreign affairs is specifically denied to the states by the Constitution. This power is reserved for the federal government, which is responsible for managing diplomacy, treaties, and international relations. The framers of the Constitution recognized that allowing individual states to negotiate their own foreign policies could lead to conflicts and inconsistencies that would undermine national unity and security.

In contrast, the other options represent powers that states are either allowed to exercise or manage under certain conditions. States can levy taxes, establish state militias, and create their own constitutions, as long as they do not conflict with federal laws and the U.S. Constitution. The limitation on states regarding foreign affairs illustrates the centralization of power in matters critical to national interests and unity.