Sanctions dominate headlines, but the machinery behind them is rarely explained. This explainer walks through how economic sanctions actually work: the laws they rest on, the agencies that run them, the instruments in the toolbox, what happens when a person or bank is designated, how violations are punished, and the exits, licenses, humanitarian carve-outs and delisting. Descriptive throughout: what the machinery does, documented from official sources.
Legal foundations in the United States: IEEPA and the National Emergencies Act
Most modern US sanctions rest on two statutes passed in the 1970s. The National Emergencies Act of 1976 (NEA) sets the procedure: the President must formally declare a national emergency, report to Congress, and renew the declaration annually. The International Emergency Economic Powers Act of 1977 (IEEPA) supplies the substantive power: once an emergency is declared with respect to an "unusual and extraordinary threat" originating substantially outside the United States, the President may regulate, block, or prohibit a wide range of economic transactions and freeze property subject to US jurisdiction. In practice, a sanctions program begins with an executive order invoking IEEPA, which the Treasury Department then translates into detailed regulations codified in Title 31 of the Code of Federal Regulations. The Congressional Research Service reports that presidents have invoked IEEPA in dozens of emergency declarations since 1977, with emergencies lasting nearly a decade on average. Congress also legislates sanctions directly (for example, CAATSA in 2017), and the older Trading with the Enemy Act of 1917 remains the basis for parts of the Cuba embargo. Courts have generally read IEEPA's delegation of economic authority broadly.
Legal foundations beyond the US: UN Charter Chapter VII, EU treaties, UK SAMLA 2018
United Nations sanctions flow from Chapter VII of the UN Charter. After the Security Council determines under Article 39 that a threat to the peace exists, Article 41 lets it decide on "measures not involving the use of armed force," which member states are obliged to carry out. In the European Union, sanctions (formally "restrictive measures") are adopted in two steps: the Council of the EU first agrees, by unanimity, a Common Foreign and Security Policy decision under Article 29 of the Treaty on European Union; where the measures include asset freezes or other economic restrictions, the Council simultaneously adopts a regulation under Article 215 of the Treaty on the Functioning of the European Union, which is directly applicable law in every member state. The United Kingdom, after leaving the EU, built its own framework through the Sanctions and Anti-Money Laundering Act 2018 (SAMLA). SAMLA empowers ministers to make sanctions regulations, such as the Russia (Sanctions) (EU Exit) Regulations 2019, to implement UN obligations or to pursue UK foreign-policy purposes, and it sets out designation criteria, licensing powers, and review rights for designated persons.
Who implements sanctions
In the United States, the Treasury Department's Office of Foreign Assets Control (OFAC) administers and enforces most financial sanctions, maintains the Specially Designated Nationals (SDN) list, issues licenses, and writes program regulations. The Commerce Department's Bureau of Industry and Security (BIS) administers export controls under the Export Administration Regulations, and the State Department, through its sanctions offices, provides foreign-policy guidance, negotiates with partners, and administers certain statutory designations. In the EU, the Council adopts the measures, the European Commission monitors uniform application, and enforcement is carried out by national authorities in each member state. In the UK, HM Treasury's Office of Financial Sanctions Implementation (OFSI) implements and enforces financial sanctions and issues licenses, while the Foreign, Commonwealth and Development Office leads on policy and designations. At the United Nations, each sanctions regime is administered by a sanctions committee composed of all fifteen Security Council members, typically chaired by an elected member. Panels of experts, small teams appointed by the Secretary-General, monitor implementation, investigate reported violations, and report to the committees. UN sanctions have no self-executing enforcement arm; member states must transpose and enforce them through domestic law.
The core instruments: embargoes, asset freezes, sectoral and secondary sanctions
Sanctions programs assemble different instruments depending on the target. Comprehensive embargoes prohibit virtually all trade and financial dealings with a jurisdiction; US examples include the programs covering Cuba, Iran, North Korea, and the Crimea region of Ukraine. (The comprehensive US program on Syria was revoked by executive order in June 2025, with targeted Syria-related designations remaining in place.) Far more common today are targeted ("smart") measures aimed at specific persons and activities. Asset freezes, blocking, in US terminology, apply to individuals and entities placed on lists such as OFAC's SDN list, the EU's consolidated list, or the UK sanctions list. Sectoral measures restrict defined dealings with named firms in particular industries without blocking them entirely; for example, prohibitions on new debt or equity transactions with listed energy or financial companies. Secondary sanctions, used mainly by the United States, expose non-US persons to designation or loss of access to the US market for specified dealings with sanctioned parties, even absent any US nexus in the underlying transaction. Travel bans deny visas and entry to listed individuals, and arms embargoes prohibit the supply of weapons and related materiel, both are standard components of UN and EU regimes. Most programs combine several instruments and adjust them over time.
Infrastructure tools: export controls, SWIFT exclusion, and price caps
Several instruments work through trade and financial infrastructure rather than asset freezes. US export controls are administered by BIS under the Export Administration Regulations. The Entity List (Supplement No. 4 to Part 744 of the EAR) names foreign parties for whom exports, reexports, or in-country transfers of specified items require a BIS license, often reviewed under a presumption of denial; related tools extend US jurisdiction to some foreign-made products of US technology. Financial-messaging exclusion cuts banks off from the SWIFT network that most cross-border payment instructions travel through: Council Regulation (EU) 2022/345 prohibited providing "specialised financial messaging services" to seven listed Russian banks from 12 March 2022, with later rounds adding more institutions. The oil price cap, introduced in December 2022 by a coalition of the G7, the EU, and Australia, takes a service-based approach: coalition firms may provide maritime transport, insurance, and related services for Russian-origin crude only if the oil is sold at or below a set cap (initially $60 per barrel), with an attestation-based safe harbor for service providers. OFAC, OFSI, and EU authorities each published parallel guidance implementing the cap.
How an SDN designation works in practice
When OFAC designates a person or entity as a Specially Designated National, all of that party's property and interests in property that are in the United States, or that come within the possession or control of a US person anywhere, are "blocked": they must be frozen, reported to OFAC, and cannot be transferred or dealt in. US persons, US citizens and permanent residents wherever located, entities organized under US law and their foreign branches, and anyone physically in the United States, are generally prohibited from transacting with the SDN. Under OFAC's 50 Percent Rule, any entity owned 50 percent or more, directly or indirectly, in the aggregate by one or more blocked persons is itself blocked automatically, even if it is not named on the list; the rule turns on ownership, not control. Designations also propagate through the payments system. Because most dollar transactions clear through correspondent accounts at US banks, a dollar payment involving an SDN typically cannot be processed anywhere in the world, and non-US banks frequently decline even non-dollar business with listed parties to manage their own exposure, a practice often described as de-risking.
Enforcement and penalties
US sanctions violations carry both civil and criminal exposure. Civil liability is strict, no intent is required, and OFAC assesses penalties under its Economic Sanctions Enforcement Guidelines (Appendix A to 31 CFR Part 501), weighing factors such as willfulness, harm, compliance programs, and voluntary self-disclosure. Willful violations can be prosecuted criminally under IEEPA, with fines and imprisonment for individuals. Two documented cases illustrate the scale. In 2014, BNP Paribas agreed to plead guilty to conspiring to violate IEEPA and the Trading with the Enemy Act and to pay $8.97 billion in total financial penalties, after moving more than $8.8 billion through the US financial system for Sudanese, Iranian, and Cuban sanctioned entities between 2004 and 2012; the resolution also suspended part of the bank's dollar-clearing business for a year. In 2019, Standard Chartered Bank agreed to a $639 million settlement with OFAC as part of a roughly $1.1 billion combined resolution with US and UK authorities over transactions involving Iran and other sanctioned jurisdictions. In the UK, OFSI can impose civil monetary penalties for financial-sanctions breaches on a strict-liability basis, a standard established by the Economic Crime (Transparency and Enforcement) Act 2022, applying its published enforcement and monetary penalties guidance, alongside potential criminal prosecution.
Exemptions and off-ramps: licenses, humanitarian carve-outs, delisting
Sanctions prohibitions are qualified by authorizations and exit routes. A general license, published by OFAC (or OFSI in the UK), permits an entire class of otherwise prohibited transactions without any application, common examples authorize humanitarian transactions, wind-down periods, or legal fees. A specific license is a written authorization issued case by case in response to an application when no general license applies. Some activities, such as trade in informational materials under US law, are exempt by statute. Humanitarian carve-outs have been standardized at the UN level: Security Council Resolution 2664 (2022) created a standing exemption from UN asset freezes for funds and services necessary for humanitarian assistance and basic human needs, which the US, EU, and UK then mirrored in their own programs. Delisting procedures provide the off-ramp. Under 31 CFR 501.807, a listed person may petition OFAC for reconsideration, arguing that the basis for listing was insufficient or that circumstances have changed; OFAC reviews the record and issues a written decision. At the UN, petitioners on the ISIL (Da'esh) and Al-Qaida list may apply to an independent Ombudsperson established by Resolution 1904 (2009), while EU and UK designations can be challenged in court.
How US, EU, UK, and UN measures fit together
The four systems interlock but remain legally distinct. UN Security Council sanctions bind all member states, which must implement them domestically, the EU does so through Council regulations, the UK through regulations under SAMLA 2018, and the US through executive orders and OFAC regulations. Outside the UN framework, the US, EU, and UK adopt autonomous measures, and since 2022 the Russia-related programs have been closely coordinated among G7 members, the EU, and partners such as Australia, most visibly in the jointly administered oil price cap. Coordination happens through diplomatic channels: the State Department's sanctions offices build international support and align designations with allies, the EU's High Representative and member states propose parallel listings, and technical bodies exchange evidence for designation packages. Alignment is nonetheless incomplete by design and by procedure. Each jurisdiction applies its own legal tests and evidentiary standards, so lists do not fully overlap; EU measures require unanimity among 27 member states and periodic renewal; and US secondary sanctions reach conduct with no US nexus, which the EU and UK generally do not assert. Businesses operating across these jurisdictions therefore typically screen against all applicable lists simultaneously.
About this explainer
This explainer is descriptive, not evaluative: it explains how the machinery works, drawing on official and primary sources, every section links to the documents it relies on. Factual claims, list memberships, case figures and legal citations were independently re-checked against those sources before publication. It is part of the Sanctions and Money Laundering Studies program, which also maintains a verified, year-by-year catalog of major sanctions on Russia, China and Iran.