Which act provides the legal authority for many sanctions and embargoes?

The International Emergency Economic Powers Act is the correct answer because it grants the President of the United States the authority to impose economic sanctions and embargoes during times of national emergency that threaten the foreign policy, national security, or economy of the United States. This act enables the government to regulate foreign commerce in times of crises, allowing for swift and effective responses to international situations that may arise.

The other acts mentioned, while related to trade and economic relations, do not specifically focus on the imposition of sanctions and embargoes. For example, the Export Control Reform Act deals more with managing exports for national security reasons, the Foreign Assistance Act is primarily about providing aid to foreign nations, and the Trade Expansion Act facilitates trade negotiations and agreements rather than imposing restrictions. Therefore, the International Emergency Economic Powers Act stands out as the key legislation providing the legal framework for economic sanctions and embargoes.