Lex Fori

In private international law (conflict of laws), lex fori denotes the internal law of the jurisdiction in which a case is being heard. It is contrasted with lex causae (the law governing the substance of the dispute), lex loci contractus (law of the place where a contract was made), and lex loci delicti (law of the place where a tort occurred).

Courts almost universally apply lex fori to procedural matters—rules of evidence, pleadings, limitation periods (in some jurisdictions), service of process, and court costs—even when the substantive issues are governed by foreign law. The rationale is practical: a judge cannot reasonably be expected to run their courtroom according to the procedural code of another state.

The line between procedure and substance, however, is contested. Common-law systems historically classified statutes of limitation as procedural (and thus lex fori), while civil-law systems treat them as substantive. The UK shifted this position in the Foreign Limitation Periods Act 1984, generally applying the limitation rules of the lex causae. Similarly, the EU's Rome I Regulation (593/2008) on contractual obligations and Rome II Regulation (864/2007) on non-contractual obligations harmonised choice-of-law rules across member states, narrowing the residual scope of lex fori for substance while preserving it for procedure (Rome II Art. 1(3)).

Lex fori also surfaces in:

• Public policy exceptions (ordre public): a forum court may refuse to apply foreign law that violates its fundamental values.
• Renvoi debates, where the lex fori's conflict rules point to another system.
• Characterisation: deciding whether an issue is "contract" or "tort" is generally done under lex fori.

For international arbitration, the concept is modified—the lex arbitri (law of the seat) replaces the traditional forum, though arbitrators still distinguish procedural from substantive law in much the same way.