Retrospect and relation of laws

XLVII. There is also another way of supplying cases omitted; viz., when one law is made upon another, and brings the cases omitted along with it. This happens in those laws or statutes, which, according to the common phrase, look backward. But laws of this kind are to be seldom used, and with great caution; for a Janus-face is not to be admired in the law.

XLVIII. He who captiously and fraudulently eludes and circumscribes the words or intention of a law, deserves to be hampered by a subsequent law. Whence, in fraudulent and evasive cases, it is just for laws to carry a retrospection, and prove of mutual assistance to each other; so that he who invents loopholes and plots the subversion of present laws, may at least be awed by future.

XLIX. Such laws as strengthen and confirm the true intentions of acts and instruments against the defects of forms and solemnities, very justly include past actions; for the principal fault of a retrospective law is, its causing disturbance; but these confirming laws regard the peace and settlement of transactions. Care, however, must be had not to disturb things once adjudged.

L. It should be carefully observed, that not only such laws as look back to what is past invalidate former transactions, but such also as prohibit and restrain things future, which are necessarily connected with things past: so, if any law should prohibit certain artificers the sale of their wares in future, this law, though it speaks for hereafter, yet operates upon times past, though such artificers had then no other lawful means of subsisting.

LI. All declaratory laws, though they make no mention of time past, yet are, by the very declaration itself, entirely to regard past matters; for the interpretation does not begin with the declaration, but, as it were, is made contemporary with the law itself. And therefore declaratory laws should not be enacted, except in cases where the law may be retrospected with justice. And so much for the uncertainty of laws, where the law is extant. We proceed to the other part, where the laws, though extant, are perplexed and obscure.