Plain-language explanation.
International law is the body of rules governing relations between states and other actors — covering treaties, customary law, diplomatic relations, armed conflict, human rights, and international courts.
Core concepts and standard treatment.
Core international law covers sources and subjects (Article 38 ICJ Statute — treaties, customary international law — state practice and opinio juris; jus cogens — peremptory norms — torture, genocide, slavery — erga omnes; statehood — Montevideo criteria; recognition — declaratory vs constitutive; VCLT 1969 — pacta sunt servanda; reservations — Arts. 19-23; treaty interpretation — textual, object and purpose, travaux), international human rights law (UDHR 1948; nine core UN treaties — ICCPR, ICESCR, CAT, CERD, CEDAW, CRC, CRPD; treaty bodies — periodic reporting — individual communications; ECHR — Strasbourg Court; IACHR; ACHPR; HRC — UPR — universal periodic review — special procedures), and use of force (UN Charter Art. 2(4) — prohibition; Art. 51 — self-defence; Security Council Chapter VII — R2P Pillar 3 — Libya 2011 — Syrian veto; humanitarian intervention — Kosovo 1999 without UNSC; anticipatory self-defence — Caroline criteria; Tallinn Manual 2.0 — cyber warfare and IHL).
Deeper theory, debates and edge cases.
Advanced international law covers IHL (four Geneva Conventions 1949 — APs 1977; distinction — proportionality — precaution; prohibited weapons — CWC, BWC, Ottawa Treaty, cluster munitions — CCM; occupation law — Art. 42 Hague Regulations — Gaza legal debates; ICRC guardian of IHL), international criminal law (Nuremberg — individual criminal responsibility; Rome Statute 1998 — ICC — genocide, crimes against humanity, war crimes, crime of aggression; complementarity — admissibility; immunities — Al-Bashir — Art. 27 vs Art. 98; ICC Ukraine — arrest warrant Putin March 2023), and law of the sea (UNCLOS 1982 — 12nm territorial sea — 200nm EEZ — continental shelf; ITLOS; SCS Arbitration 2016 — Philippines v China — U-shaped line; BBNJ Agreement 2023 — high seas treaty; deep seabed mining — ISA; maritime delimitation — equidistance and special circumstances).
How it is applied in practice.
At the international law professor and FCO legal adviser level, practitioners contribute to EJIL; advise government (FCDO Legal Advisers — UK Treaty Series; Cabinet Office international law opinions — NI Protocol — breaking international law in specific and limited way; AUSA warrants on foreign states; State Department Legal Adviser); lead international criminal law practice (ICC OTP — preliminary examinations — 17 situations; Ukraine fast-tracked Art. 15; ICTY, ICTR, SCSL legacy; KSC Kosovo Specialist Chambers; IIIM Syria evidence collection); advise on multilateral treaty negotiations (UN OLA treaty section; NPT RevCon; Arms Trade Treaty; ITU cyber norms; BBNJ — PSIDS Pacific small island developing states); and contribute to international economic law (WTO dispute settlement AB reform; ICSID investment arbitration — BITs — ECT modernisation; UNCITRAL Working Group III ISDS reform — multilateral investment court proposal).