Say the ratio out loud before you open Reasoning — recalling it unprompted is exactly what the exam pays for.
Why it matters
It supplies the frame for the whole doctrine of exclusion. Before you can say when a forum will refuse to apply a proved foreign rule, you have to be clear about what the forum was doing when it applied one — and this case says.
Facts
This course cites the case for Lord Parker's statement of principle and does not set out its facts.
Held
It is not the foreign law but the forum's own law to which effect is given. Private international law is really a branch of municipal law, and there can be no branch of law in which the general policy of that law can properly be ignored.
Reasoning
Step one — restate what the forum is doing. When an Indian court applies French law it does so because an Indian rule told it to. The subject is municipal, not international: it is a branch of the civil law of the State, evolved to do justice between litigating parties in transactions or personal status involving a foreign element, and its rules differ from State to State.
Step two — draw the consequence for policy. If the operative rule is always the forum's own, the forum's general policy cannot be irrelevant to it. A system does not surrender its policy by directing recourse to another system.
Step three — hence the three exclusions. Foreign revenue laws are not enforced — Government of India v. Taylor, where tax gathering is described as a matter not of contract but of authority and administration as between the State and those within its jurisdiction. Foreign penal laws are not enforced, and the forum decides for itself whether the law is penal — Huntington v. Attrill, with Banco de Vizcaya v. Don Alfonso as a case where it was. And laws offending fundamental policy are refused, the court declining to apply a law which outrages its sense of justice and decency.
Step four — keep the doctrine narrow. In conflicts the public-policy control is deliberately narrower than in domestic law: a transaction valid by its lex causae is not to be invalidated unless its enforcement would offend a moral, social or economic principle so sacrosanct as to require maintenance at all costs and without exception.
Exam use
It opens: When will a court refuse to apply a proved foreign law? — open with this frame, then give the three classes.
Draw the distinction between exclusion and non-recognition, which is the fine point that separates a good answer from an average one: revenue and penal laws are still recognised for other purposes even though they are not enforced, so a contract designed to defraud a foreign revenue will not be enforced here.
Use it in Module 1 as well. It is the doctrinal partner of the proposition that the only law the judge applies is the lex fori and that foreign law enters as a fact — and of the rules that characterisation and the meaning of connecting factors are for the forum.
It does not decide any of the three exclusions itself; it supplies the reason why they exist.