—that is, within the three years commencing on December 10, 1938, and ending on December 10, 1941. Our opinion however is that the word “shall” in the phrase “shall prescribe in three years” does not indicate an intention that the plea of prescription was not to be available immediately after the constitutional amendment would go into effect, on December 10, 1938, as a defense to a suit filed on or after that date, for license taxes then more than three years past due. The word “shall” meant that the prescription would be available at any time after the amendment would go into effect, under Section 1 of Article XXI of the Constitution. The word “are”, in the phrase “three years from the 31st day of December in the year in which such taxes or licenses are due”, does not indicate whether the intention was that the plea of prescription would be available immediately when the amendment would go into effect, on December 10, 1938, or would not be available within three years after that date. If the framers of the amendment had intended that the plea of prescription should apply only to taxes becoming due after the amendment would go into effect, they would have used some such phrase as “shall become due”. If the framers of the amendment had used the past tense, “became due”, instead of “are due”, it might be argued that the amendment was not applicable to taxes coming due subsequent to the date on which the amendment would become effective,—December 10, 1938. The phrase “are due” was used advisedly, to make the amendment applicable to taxes which would be already three years or more past due when the amendment would go into effect, on December 10, 1938, as well as to taxes which would become due after that date. There is therefore in the wording of this amendment nothing which indicates an intention that the plea of prescription should be unavailing until the lapse of three years from the date of the amendment’s becoming “effective” under Section 1 of Article XXI of the Constitution.
When we consider that this constitutional amendment, adopted in pursuance of Act 35 of 1938, could not possibly impair the obligation of a contract, or affect any vested right except rights of the State herself, there is no reason why we should not apply the general rule of construction announced in De Armas v. De Armas, 3 La.Ann. 526, in 1848,—and affirmed only two years ago in Shreveport Long Leaf Lumber Co. v. Wilson, 195 La. 814, 197 So. 566, thus:
“Laws of prescription, and those limiting the time within which actions may be brought, are retrospective in their operation.”
But, of all of the rulés of statutory construction, the one which is most appropriate to this case is the so-called universal rule, stated in article 18 of the Civil Code, thus:
“The universal and most effectual way of discovering the true meaning of a law, when its expressions are dubious, is by considering the reason and spirit of it, or the cause which induced the Legislature to enact it.”
The cause which induced the Legislature to enact the joint resolution, Act 35 of 1938, proposing to amend the Constitution so as to put an end to the bringing of suits on stale claims for back taxes alleged to be more than three years past-due, was the disclosure in the case of State v. Standard Oil Co., 188 La. 978, loc.cit. 1034-1037, 178 So. 601, loc.cit. 619, 620, that, by certain changes made in the adoption of the Constitution of 1921, the prescription by which, under Act 148 of 1906, suits to collect delinquent license taxes were barred after the lapse of three years,—and which theretofore was applicable as well to license taxes on the occupation of severing natural resources as to license taxes on other occupations,—became inapplicable to the severance tax imposed upon natural resources under authority of the Constitution of 1921. The result of that finding was that the defendant in that case alone was condemned to pay additional taxes, or back taxes, amounting to $72,591.51 and penalties amounting to $70,323.51, or a total sum of $142,915.02, covering a period of eight years, in which these additional taxes had not been demanded. That case was decided on November 2, 1937, and the petition of the defendant for a rehearing was denied on January 10, 1938. At the same time there was pending in this court a suit against the Standard Oil Company for additional taxes on the sales of gasoline during the period from January 4, 1929, to September 30, 1937. The amount claimed in that case was $566,804.28, plus $113,360.85 for the ?0% statutory penalty, and $68,016.51 attorneys’ fees, or a total sum of $748,181.64; and, if the decision had gone against the defendant in that case,