Governments have five broad categories of foreign policy tools to work with: diplomacy, economic measures, military force, intelligence and covert operations, and public communication aimed at foreign audiences. Each instrument has its own legal framework that decides who can authorize it, under what conditions, and with what oversight. In practice they overlap. Sanctions accompany diplomatic pressure. Military posture shapes the backdrop of a negotiation. Public messaging supports all of it. The choice among them turns on the stakes, the urgency, and whether cooperation or coercion is more likely to work.
Diplomacy and Treaties
Diplomacy is the default. Governments talk before they pressure, and pressure before they fight. That work runs through bilateral conversations between two countries and multilateral forums involving many. Ambassadors at embassies and consulates keep the channels open day-to-day, even when relations are strained.
When talks succeed, they often produce a treaty, a written agreement between nations that carries legal obligations under international law.1United Nations. Vienna Convention on the Law of Treaties Treaties cover trade, arms control, environmental commitments, and much else. The UN Charter itself functions as a binding treaty among member states, setting core principles like sovereign equality and the prohibition on using force to settle disputes.2United Nations. United Nations Charter
Diplomatic channels also handle narrower legal cooperation. Extradition treaties set the rules for surrendering criminal suspects across borders. Most require dual criminality, meaning the alleged conduct must be a crime in both countries for the request to proceed.3U.S. Department of State. The Consular Role in International Extradition Without a treaty, a country generally has no obligation to hand a suspect over at all.
Economic Incentives and Pressure
Economic tools split cleanly into rewards and penalties. Governments offer financial benefits to encourage cooperation and impose financial costs to change behavior. This toolkit has expanded significantly in recent decades and now carries much of the load in disputes where military force is off the table and diplomacy alone is not enough.
Aid, Trade, and Export Financing
Foreign aid is one of the oldest instruments. The U.S. Foreign Assistance Act directs that aid to low-income countries come on favorable terms, while assistance to more developed nations should focus on helping them access private capital markets.4GovInfo. Foreign Assistance Act of 1961 Aid packages often come with conditions attached, whether policy reforms, human rights benchmarks, or economic liberalization targets.
Free trade agreements reduce tariffs and quotas among participating countries. For the United States, the goal is to open foreign markets to American exports while strengthening intellectual property protections and investor safeguards abroad.5International Trade Administration. Free Trade Agreement Overview Access to a large domestic market gives negotiators real leverage on unrelated issues. Export financing fills a narrower gap: the Export-Import Bank provides loans, guarantees, and insurance to support U.S. exports when private lenders will not.6EXIM.GOV. About EXIM
Sanctions
Sanctions are the coercive side. When the President declares a national emergency related to a foreign threat, the International Emergency Economic Powers Act grants sweeping authority to block financial transactions, freeze assets, and restrict trade involving the targeted country, organization, or person.7Office of the Law Revision Counsel. 50 USC 1702 – Presidential Authorities During armed conflict, the President can go further and confiscate property belonging to foreign persons or governments that planned or participated in attacks against the United States.
The Treasury Department’s Office of Foreign Assets Control runs these programs day-to-day, targeting foreign governments, terrorist organizations, narcotics traffickers, and entities involved in weapons proliferation, among others.8U.S. Department of the Treasury. Office of Foreign Assets Control Sanctions can be comprehensive, blocking virtually all trade with a country, or selective, hitting specific individuals and entities while leaving broader commerce alone. Selective sanctions have grown more common because they concentrate pressure on decision-makers rather than punishing a whole population.
Trade Enforcement and Investment Screening
Trade policy also works offensively. Under Section 301 of the Trade Act of 1974, the U.S. Trade Representative can investigate whether a foreign government’s policies unfairly burden American commerce and, on finding a violation of trade agreement rights or unjustifiable practices, impose tariffs, restrict imports, or withdraw trade concessions.9Office of the Law Revision Counsel. 19 USC 2411 – Actions by United States Trade Representative
Investment screening runs the other direction, controlling what flows in. The Committee on Foreign Investment in the United States reviews foreign acquisitions of American businesses and certain real estate transactions for national security concerns. The Foreign Investment Risk Review Modernization Act of 2018 broadened that authority to reach non-controlling investments and real estate near sensitive military installations.10U.S. Department of the Treasury. The Committee on Foreign Investment in the United States (CFIUS) If CFIUS identifies a threat, the President can block or unwind the transaction.
Military Force and Security Cooperation
Military capability shapes foreign policy even when no shots are fired. A credible fighting force changes the calculations of potential adversaries and reassures allies. When force does become necessary, both international and domestic law limit who authorizes it and how it can be used.
Deterrence and Mutual Defense Treaties
Deterrence works by making the cost of aggression clearly exceed any gain. It requires both real capability and a credible signal that the government is willing to use it. Mutual defense treaties formalize deterrence by committing multiple nations to respond collectively to an attack on any member. The North Atlantic Treaty provides that an armed attack against any party in Europe or North America is considered an attack against all. Bilateral treaties with the Philippines, Japan, South Korea, and Australia establish similar commitments in the Pacific, and the Rio Treaty extends collective security to the Western Hemisphere.11U.S. Department of State. U.S. Collective Defense Arrangements
When Force Is Legal Under International Law
The UN Charter sets the baseline. Member states must refrain from the threat or use of force against the territorial integrity or political independence of any other state.12United Nations. Repertory of Practice – Article 2(4) Two exceptions exist.
The first is self-defense. Article 51 preserves the right of individual or collective self-defense when an armed attack occurs, though the defending state must immediately report its actions to the Security Council.13United Nations. Repertory of Practice – Article 51 The second runs through the Council itself. Under Chapter VII, the Council can determine that a situation threatens international peace and authorize measures in response, starting with non-military steps like embargoes and severing diplomatic relations. If those prove inadequate, it may authorize member states to take military action.14United Nations. Chapter VII – Action with Respect to Threats to the Peace The veto power held by the five permanent members means this authorization is difficult to secure when any major power opposes intervention.
Arms Sales, Training, and the Leahy Law
Not every military tool involves deploying a nation’s own forces. Arms sales to allied governments strengthen their capacity to defend themselves and promote interoperability among partner militaries. U.S. law frames this as facilitating the common defense through cooperative arrangements covering equipment, training, joint research, and logistics support, with a preference for sales to countries that can equip their own forces without straining their economies.15Office of the Law Revision Counsel. 22 USC 2751 – Need for International Defense Cooperation and Military Export Controls Training programs, advisory support, and joint exercises build relationships between officer corps that carry over into crises.
Federal law also draws a hard line. The Leahy Law prohibits providing military assistance to any foreign security force unit when credible information indicates that unit has committed gross violations of human rights, specifically covering torture, extrajudicial killing, enforced disappearance, and rape committed under color of law.16Office of the Law Revision Counsel. 22 USC 2378d – Limitation on Assistance to Security Forces The prohibition can be lifted only if the Secretary of State determines that the foreign government is taking effective steps to bring the responsible individuals to justice. Vetting applies to every unit receiving U.S. assistance.
Intelligence and Covert Action
Intelligence gathering and covert operations sit in a distinct category because they are designed to remain hidden. Covert action is legally defined as activity intended to influence political, economic, or military conditions abroad where the U.S. government’s role will not be apparent or publicly acknowledged.17Office of the Law Revision Counsel. 50 USC 3093 – Presidential Approval and Reporting of Covert Actions That definition excludes routine intelligence collection, traditional diplomacy, and conventional military operations.
The safeguards are strict. The President cannot authorize covert action without a written finding that the activity is necessary to support identifiable foreign policy objectives and is important to national security. The finding must specify which agencies are authorized to participate and whether any non-government third parties are involved. No finding may authorize activity that has already occurred, and no covert action may violate the Constitution or any federal statute.17Office of the Law Revision Counsel. 50 USC 3093 – Presidential Approval and Reporting of Covert Actions Congressional intelligence committees must be notified, creating at least some external check on an inherently secretive process.
Allied intelligence cooperation multiplies what any one country can collect. The Five Eyes alliance among the United States, the United Kingdom, Canada, Australia, and New Zealand pools collection capabilities and shared analysis under classified frameworks. Public oversight of those arrangements is inherently limited.
Public Diplomacy and Strategic Communication
Informational tools try to influence foreign populations directly rather than working through government-to-government channels. The premise is that citizens who understand and broadly support a country’s values and policy goals will pressure their own government to cooperate. This soft power approach works by attraction, and its effects are gradual.
Cultural and educational exchanges are among the strongest long-term investments. The Mutual Educational and Cultural Exchange Act authorizes the President to fund exchanges of students, trainees, teachers, professors, and specialists between the United States and other countries, along with tours by performing artists and athletes, U.S. participation in international festivals, and visits by foreign leaders and professionals.18U.S. Government Publishing Office. Mutual Educational and Cultural Exchange Act of 1961 A foreign official who studied in the United States carries that perspective through a career.
Strategic communication operates on a faster clock. State-sponsored media, digital campaigns, and rapid-response messaging try to frame international narratives and counter disinformation. Adversaries use many of the same tools, and the line between public diplomacy and propaganda is contested. Effectiveness depends on credibility: audiences who trust the source engage with the message, and those who perceive manipulation push back.
Domestic Checks on U.S. Foreign Policy
These tools are not exercised in a vacuum. The Constitution divides foreign affairs power between the executive and legislative branches, and several statutes impose procedural requirements and substantive limits on presidential action.
Treaties vs. Executive Agreements
The Constitution requires the Senate to approve any treaty by a two-thirds vote of senators present. The framers gave the Senate this role to ensure that binding international commitments reflected broad political consensus.19U.S. Senate. About Treaties The threshold is deliberately high.
Since World War II, presidents have relied increasingly on executive agreements, which are binding under international law but bypass the two-thirds ratification process.20U.S. Senate. About Treaties Executive agreements now vastly outnumber formal treaties, and that shift has moved foreign policy authority toward the executive branch.
The War Powers Resolution
The War Powers Resolution is the sharpest congressional check on military action. When a president introduces armed forces into hostilities or situations where hostilities are imminent, the administration must notify Congress in writing within 48 hours, explaining the circumstances, the legal authority for the action, and the expected scope and duration.21Library of Congress. War Powers Resolution, 50 USC 1541-1548
A 60-day clock starts from the date that report is submitted. Unless Congress declares war, enacts specific authorization, or extends the deadline by law, the president must withdraw the forces. A 30-day extension is available only if the president certifies in writing that the safety of the troops requires it during withdrawal.21Library of Congress. War Powers Resolution, 50 USC 1541-1548 Congress can also direct removal of forces at any time through legislative action. Presidents of both parties have contested the Resolution’s constitutionality, and the 60-day clock has never been fully tested in court, but the notification and reporting requirements are now standard practice.