Which of the following describes a power that cannot be exercised by the federal government?

The option indicating the establishment of public schools pertains to a power that is primarily reserved for the states rather than the federal government. In the framework of federalism established by the U.S. Constitution, education is traditionally viewed as a state responsibility. The Tenth Amendment underscores this by reserving powers not delegated to the federal government to the states or the people.

In contrast, making treaties, regulating interstate commerce, and declaring war are powers explicitly granted to the federal government by the Constitution. The federal government has the authority to engage in international relations and stability through treaties and has regulatory powers over commerce that crosses state boundaries. Moreover, only the federal government can declare war, reflecting its role in national defense and military operations.

Thus, establishing public schools is a clear example of a power that cannot be exercised by the federal government, making this choice the accurate response to the question.