Mr. Justice Field

delivered the opinion of the court. He stated the facts in the foregoing language, and continued:

In the case of Louisiana v. Mayor of New Orleans, 109 U. S. 285, we held that the right to reimbursement for damages caused by a mob or riotous assemblage of people in that city, was not founded upon any contract between the corporation and the parties injured; that its liability for the damages was created by law, and could be withdrawn or limited at the pleasure of the legislature.; that its creation was merely a measure of policy, and its character was not changed by the fact that the amount of damage sustained in. any particular ease was ascertained and established by a judgment in favor of the sufferer. So when the question arose as to the.validity of legislation changing the rate of taxation by which funds could be obtained to meet a judgment in such case, the court looked beyond the judgment to the causes upon which it was founded. As the contract clause of the Constitution was intended to secure the observance of good faith in the stipulation of parties against State action, it could not be invoked when no such stipulation existed, and therefore not against legislation which interfered merely with the enforcement of claims for damages from the violence of mobs or of judgments upon such claims.

It was, therefore, entirely within the competency of the Supreme Court of Louisiana to authorize an inquiry into the cause of action On which the judgment of Nelson was rendered, when he'prayed for its enforcement by proceedings which were authorized by legislation existing at its date, but subsequently repealed. Whether -such repeal was effectual to deprive him of the process prayed, depended upon the question whether the judgment was founded upon a contract, the obligation of which the State was prohibited from impairing. By the obligation of a contract is meant the means which, at the time of its creation, the law affords'for its enforcement. The *721 usual mode by which municipal bodies obtain the funds to meet their pecuniary engagements is taxation. Accordingly, when a contract is made upon the faith that taxes will be levied, legislation repealing or modifying the taxing power of the corporation, so as to deprive the holder of the contract of all adequate and efficacious remedy, is within the constitutional inhibition.

The inquiry, however, which may be thus instituted into the nature of the original cause of action, does not, where the judgment ivas rendered upon a contract, authorize a re-examination of the validity of the contract, or of the propriety of the judgment. That would involve a retrial of the case. Here the inquiry disclosed the fact that the judgment of Nelson was founded upon, treasury warrants issued by the Parish of. St. Martin, in favor of the municipal authorities of New Iberia, for $4,500, for the building of a bridge over a bayou within the limits of the corporation, made payable out of certain funds, the.proceeds of taxes for particular years. It may be that the funds mentioned were merely such as the authorities intended to apply to the payment of the warrants, and were not designed to be any limitation upon the right of the holder to payment for the construction of the bridge if such funds did not exist. So the district court would seem • to have thought, as its .judgment was general, that the plaintiff recover the amount absolutely from the parish, and this judgment had become final before the application for the writ of mandamus. The absolute liability of the parish upon such warrants was therefore no longer an open question, and the inquiry whether the judgment was founded upon a contract was answered. Farther testimony on the subject was irrelevant and incompetent. The Supreme Court, however, held that the designation of the funds out of which the warrants were to be paid rendered the parish liable only if the funds were sufficient, notwithstanding the terms of the judgment. Its conclusion in this respect was wholly unauthorized, because founded upon evidence which it could not legitimately consider. The judgment being absolute, and the plaintiff therein being by law entitled at the time to a decree that the assessing and collecting officers of the parish should assess and collect a tax suffi *722 cient to pay it, and such decree having been entered, and those officers having failed in their duty, the relatop was entitled to the writ prayed. The Code of Procedure of Louisiana declares that the writ may be directed to public officers to compel them to fulfil any of the duties attached to their office, or which may be legally required - of them. Article 834. There can be no doubt, therefore, that under this law the writ should have been granted.

The position of the court that the relator was not entitled to •the writ because the decree accompanying the judgment contemplated a levy of the tax in 1873 according to the assessment roll of that year, is without force. He was entitled, and the party succeeding to his interest is entitled to a writ commanding the levy and collection of a sufficient tax to pay the judgment, according to the assessment roll of the year in which. the levy is made, at any time until the judgment is satisfied ; the right to demand the tax not depending upon the valuation of the taxable property for any year for general purposes. Such right was not only assured by the law in force when the contract was made, but was expressly declared in the decree accompanying the judgment and forming part of it. It is difficult to conceive a plainer case for the relief prayed.

The decree must be reversed, with directions to the Supreme Court to affirm the judgment of the Third District Court a/wa/rding the mandamus prayed / and it is so ordered.