In a closed economy, the primary restriction the government would impose is that the government would prohibit trade with other nations. This means that there would be no imports or exports of goods and services, effectively isolating the economy from the global market.
Without international trade, the domestic market is solely reliant on local resources, production capabilities, and consumption. This can lead to several outcomes, such as self-sufficiency but also potential inefficiencies or shortages of goods that are not produced locally.
While options such as setting prices for imported goods or preserving traditional customs may be considerations in other economic frameworks, they would not be applicable in a strictly closed economy where borders are closed to trade entirely. Therefore, the most accurate answer is prohibiting trade with other nations.