Lex fori means, in practical terms, the law of the court seised of the case. In cross‑border disputes it is the forum’s own law governing procedure (e.g. jurisdiction and service, pleadings and evidence, interim measures, costs, security for costs, enforcement steps) and the forum’s conflict‑of‑laws rules used to identify the applicable substantive law (lex causae). The term is a descriptive expression of private international law, recognised in case law rather than defined by statute.Key features include:- Characterisation and classification of issues as procedural or substantive are made by the forum under its lex fori.- Overriding mandatory rules and public policy of the forum may apply irrespective of the lex causae.- If the forum’s choice‑of‑law rules point to its own law, lex fori also supplies the substantive rules.Limitation periods illustrate the procedural/substantive divide: historically treated as procedural (and so lex fori), but now generally substantive when foreign law applies-see the Foreign Limitation Periods Act 1984 (UK, including Scotland and Northern Ireland) and the Statute of Limitations (Amendment) Act 1991 (Ireland).Usage is broadly consistent across England & Wales, Scotland, Northern Ireland and Ireland. The forum applies its own conflicts framework (e.g. Rome I/Rome II-retained in the UK; directly applicable in Ireland).