"Reimposed" means the earlier UN Security Council measures from resolutions 1696, 1737, 1747, 1803, 1835 and 1929 were restored and again legally binding as they were before Resolution 2231 (2015) terminated them. The reimposition occurred under the JCPOA/Resolution 2231 'snapback' process: France, Germany and the UK notified the Security Council (28 Aug 2025) that Iran was in "significant non‑performance" (paragraph 11 of 2231), the Council failed to adopt a resolution to keep the terminations in effect within the 30‑day window, and therefore, per paragraph 12 of 2231, the earlier resolutions automatically re‑applied on 27 Sept 2025.
The E3 (France, Germany, UK) and IAEA reports cited a range of breaches as "significant non‑performance": expanded and accelerated uranium enrichment (including higher‑enrichment levels and more advanced centrifuges), development of enrichment capacity and related R&D beyond JCPOA limits, steps toward plutonium separation/reprocessing, and restrictions on IAEA access and safeguards cooperation. (Exact lists appear in the E3 notification and successive IAEA reports.)
"Country‑ and sector‑specific technical security assistance" refers to tailored U.S. help to individual countries or to particular economic/transportation sectors (for example customs, maritime interdiction, financial compliance, export controls, cargo screening, sanctions compliance systems) — training, equipment, intelligence‑sharing, and legal/technical advice to detect and stop prohibited transfers to/from Iran.
Seizure of prohibited cargo is carried out by national authorities (coast guards, navies, customs, law‑enforcement) under their domestic law and international law (including UN authorizations and maritime interdiction regimes). States inspect, detain and divert suspect ships/aircraft or seize cargo flagged/manifesting prohibited items; enforcement typically involves the flag State, port State, and enforcing State agencies and may be coordinated through UN bodies and partner coalitions.
Enforcing travel bans and global asset freezes is primarily the responsibility of individual Member States under their domestic laws (immigration/visa controls, financial regulatory and sanctions regimes) and national authorities (border agencies, financial intelligence units, central banks). The UN provides listings and guidance, but implementation—denying entry, freezing accounts, reporting—is done by states and their financial oversight bodies.
Verification mechanisms include: IAEA safeguards and reporting on Iran's nuclear activities; UN Secretariat/Security Council monitoring and six‑monthly reports; national export‑control and customs enforcement reporting; sanctions committees and panels of experts; and peer‑review/technical assistance processes (e.g., FATF engagement). These bodies collect evidence, report non‑compliance, and advise the Council.
Consequences for Member States that fail to implement UNSCRs are limited: the Security Council can take diplomatic, political or further measures (naming, sanctions, referral to committees), and individual states may face bilateral pressure, loss of cooperation or assistance, or Council‑adopted measures if their non‑implementation is deemed a threat to peace. There is no automatic UN penalty system for implementation lapses by Member States; enforcement depends on Council action and national compliance mechanisms.