Consuetudo pro lege servatur - "Custom is held as law". Where no laws apply to a given situation, the customs of the place and time will have the force of law.⏎
De minimis non curat lex - "The law does not concern itself with the smallest things". There must be a minimal level of substance or impact in order to bring a legal action.⏎
Contra non valentem agere nulla [or non] currit praescriptio - A statute of limitation does not run against those who cannot act; this is the basis of the American discovery rule limiting prescriptive limitation periods.⏎
Delegatus non potest delegare - That which has been delegated cannot delegate further.⏎