Which of the following is a limit on the powers of the states?

The restriction that "no state shall enter into treaties" is indeed a limit on the powers of the states as outlined in the U.S. Constitution. Article I, Section 10 explicitly prohibits states from entering into any agreements or treaties with foreign governments, unless expressly authorized by Congress. This limit helps maintain a unified national foreign policy and prevents conflicts in international relations that could arise from individual states acting independently.

In contrast, the other options either describe actions that states can undertake (such as holding elections) or are inaccurately portrayed. For instance, states do have the authority to impose taxes and regulate commerce within their borders, as long as they do not conflict with federal laws. Therefore, the provision regarding treaties is crucial for ensuring that states do not infringe upon the federal government's powers and maintain the integrity of national sovereignty.