Thus we would again emphasise: the teaching of the Kirkpatrick case (and the cases which follow it) is not to do with any difference, were there to be any, between concepts of validity, legality, effectiveness, unlawfulness, wrongfulness, and so on. Validity (or invalidity) is just a useful label with which to refer to a congeries of legal concepts, which can be found spread around the cases. Similarly, the word "challenge" is not sacrosanct: the cases refer to the prohibition on adjudication, sitting in judgment on, investigation, examination, and so on. What the Kirkpatrick case is ultimately about, however, is the distinction between referring to acts of state (or proving them if their occurrence is disputed) as an existential matter, and on the other hand asking the court to inquire into them for the purpose of adjudicating upon their legal effectiveness including for these purposes their legal effectiveness as recognised in the country of the forum. It is the difference between citing a foreign statute (an act of state) for what it says (or even for what it is disputed as saying) on the one hand, something which of course happens all the time, and on the other hand challenging the effectiveness of that statute on the ground, for instance, that it was not properly enacted, or had been procured by corruption, or should not be recognised because it was unfair or expropriatory or discriminatory. As to the last possibilities, there can be a still further distinction to be made between the act of state which cannot be challenged for its effectiveness despite some alleged unfairness, and the act of state which is sufficiently outrages or penal or discriminatory to set up the successful argument that it falls foul of clear international law standards or English public policy and therefore can be challenged."