Morphy, J.

This appeal is taken from a judgment sustaining an opposition of the heirs-at-law of the late Augustin Deyraud to an account filed by his testamentary executors, on the ground that they were improperly charged in said account with the tax of ten per cent imposed by the law of the 26th of March, 1842, on property inherited by non-resident aliens; that this law should not be made to apply to successions opened before its promulgation ; and that their rights as heirs of the deceased, having vested on the 9th of May, 1841, when Deyraud died, they are not liable to pay this tax. It is urged by the Attorney General, who prosecutes this appeal on behalf of the State, that the tax is imposed on the amount of all successions belonging to foreigners, without reference to the time of the opening of such successions ; that the estate of Deyraud being in course of liquidation, and these heirs having come forward to claim it only in August, 1844, they are subject to the tax. This case cannot be distinguished from that of the Succession of Pierre Oyon. As we, there, said, it is a sound rule of construction never to consider laws as applying to cases which arose previous to their passage, unless the legislature have, in express terms, declared such to be their intention. They might, indeed, have imposed a tax on all sums to be paid to aliens not residing in the State, without reference to the opening of the successions, from which they may be entitled to receive said sums; but when such intention is not clearly and unequivocally ex*359pressed, we are bound to suppose that, according to the ordinary rules of legislation, they intended to provide for the future, and not to affect, in any way, rights previously acquired. On a re-examination of the law of 1842, we can come to no other conclusion. Its terms are prospective, and embrace, in our opinion, only cases in which non-resident aliens have become entitled to successions opened after its promulgation.

Judgment affirmed.