Taken from Blackstone’s Commentaries Volume I pp.90-91.
‘9. Acts of parliament derogatory from the power of subsequent parliaments bind not. So the statute 11 Hen. VII. c. 1, which directs that no person for assisting a king de facto shall be attainted of treason by act of parliament or otherwise, is held to be good only as to common prosecutions for high treason; but will not restrain or clog any parliamentary attainder.
Because the legislature, being in truth the sovereign power, is always of equal, always of absolute authority: it acknowledges no superior upon earth, which the prior legislature must have been, if its ordinances could bind a subsequent parliament. And upon the same principle Cicero, in his letters to Atticus, treats with a proper contempt these restraining clauses, which endeavour to tie up the hands of succeeding legislatures. “When you repeal the law itself, (says he,) you at the same time repeal the prohibitory clause, which guards against such repeal.”
10. Lastly, acts of parliament that are impossible to be performed are of no validity: and if there arise out of them collaterally any absurd consequences, manifestly contradictory to common reason, they are, with regard to those collateral consequences, void.
I lay down the rule with these restrictions; though I know it is generally laid down more largely, that acts of parliament contrary to reason are void. But if the parliament will positively enact a thing to be done which is unreasonable, I know of no power in the ordinary forms of the constitution that is vested with authority to control it: and the examples usually alleged in support of this sense of the rule do none of them prove, that, where the main object of a statute is unreasonable, the judges are at liberty to reject it; for that were to set the judicial power above that of the legislature, which would be subversive of all government. But where some collateral matter arises out of the general words, and happens to be unreasonable; there the judges are in decency to conclude that this consequence was not foreseen by the parliament, and therefore they are at liberty to expound the statute by equity, and only quoad hoc disregard it.
Thus if an act of parliament gives a man power to try all causes, that arise within his manor of Dale; yet, if a cause should arise in which he himself is party, the act is construed not to extend to that, because it is unreasonable that any man should determine his own quarrel. But, if we could conceive it possible for the parliament to enact, that he should try as well his own causes as those of other persons, there is no court that has power to defeat the intent of the legislature, when couched in such evident and express words, as leave no doubt…’