delivered the opinion of the court:
The bond .in question was executed under the provisions of the act of 1894, and the only question we-are required to determine is, whether the act of 1905 in any manner affects the right of the plaintiffs to-resort to the bond. If it does, then it is because the-latter act operates retrospectively. In behalf of defendants in error it is contended that the forum and procedure are governed by the amendatory -act, and that the action is premature, the contract as yet not having been completed.
*431Legislative enactments will not be construed as retrospective in their operation, even when permissible, unless it is clear they were intended to do so. This rule ought especially to be adhered to when such a construction will alter the pre-existing situation of parties or will affect or interfere with their antecedent rights. It is founded on the soundest principles of public policy, and its reason is manifest. Every citizen is presumed to know the law, and to enter into business engagements in accordance with its provisions. It would be manifestly unjust, even in cases where a legislative body is empowered to enact laws to some extent retroactive in effect, to take away pre-existing rights, even so far as the remedy only is concerned by judicial construction 'of a doubtful statute, unless it is clear that such is its purpose. — Pittinger v. Pittinger, 28 Colo. 308; Edelstein v. Carlile, 33 Colo. 54; Denver, S. P. & P. Ry. Co. v. Woodward, 4 Colo. 162; Harker v. Scudder, 15 Colo. App. 69; Jones v. Stockgrowers’ Nat’l Bank, 17 Colo. App. 79; United States v. Heth, 3 Cranch 399.
Without expressing an opinion on the power of Congress to pass an act which affected the substantial rights of parties in bonds given under the original act of 1894. it is clear from a comparison of the two acts, if the later is given a retrospective effect, that it works a radical change in the rights of plaintiffs, to their great detriment. Under the act of 1894 the plaintiffs could bring suit in any court of competent jurisdiction upon default of the contractor to pay what it might be owing them for labor performed and materials furnished in executing the contract, and prosecute the same to final judgment and execution. By the amendment, if it applies, suit can only be brought in the first instance by the United States, and plaintiffs would only have the right' to interven? and have their claims adjudicated in such action and judgment ren*432dered thereon, subject, however, to the priority and claim of any judgment which might be rendered in favor of the Government upon the bond, that is, they are limited in the relief which may be given them to what is left after the claim of the Government is satisfied. If the United States fails to bring a suit upon the bond, then plaintiffs could only maintain an action in the circuit court of the United States for the district of Colorado, and then only after the expiration of six months from the time of the completion of the contract and final settlement thereon. This might compel them to wait for years before an action could be instituted by them, where, before, they had the right to sue upon the bond, to recover what the contractor was owing them, immediately upon its default. Manifestly, these changes in their rights are so radical and unjust, that the statute should not be given a construction which so alters their rights unless it is clear that it was the purpose of Congress in enacting the amendment to do so.
But the statute is not susceptible of a construction which would bring about such unjust results. Its language Is prospective. It provides that "Hereafter any person or persons entering Into a formal contract with the United States, etc.” Clearly, this applies to the future. The amendment is not confined to procedure, if the limitation as to the forum where such suit can be brought on the bond can be regarded as a matter of procedure, but deals with substantive rights. That is to say, on the bond contemplated by the amendment, the United States is given a preference over all other creditors, and the right of laborers and material men to sue in their own behalf is suspended until after the completion of the contract and final settlement, and for six months thereafter, during which period the United States alone can sue upon the bond. These various provisions are all contained in one section; and if Con*433gress had intended that they should govern the rights of parties in bonds executed under the act of 1894, it is reasonable to conclude that it would have still further amended the original act by providing in plain language that the amendment should apply to such bonds, and not leave it, as it now reads when fairly construed, confined to those executed after the amendment. We think the amendment has no application whatever to the bond, the obligations of which the plaintiffs are seeking to enforce by their action.
This conclusion, in our judgment, is fully supported by Struthers, Wells & Co. v. United States, 209 U. S. 306. Counsel for defendants in error contend that this case is distinguishable from the one at bar for the reason it appears that the rights of the plaintiffs in that action had fully accrued prior to me enactment of the amendment of 1905, and that as it does not appear from the complaint in this action that the rights of plaintiffs had attached prior to the date when the amendment took effect, that the case is not in point. What the complaint may disclose in this respect we do not regard as material. The turning point in the case is the date of the execution of the bond. It is true that in the Struthers case it is said: “That Congress did not intend that the amendment should apply to cases where the bond had already been executed, the work done, the respective rights of the parties settled, and the cause of action already in existence.”
We do not understand, however, that the amendment was held inapplicable on this state of facts alone. In concluding the opinion it is said:
“Viewing the whole section, we think Congress meant that only in future cases should the provisions of the amendment apply, although some trifling portion of those provisions might be regarded technically as in the nature of procedure. It is, therefore, wiser *434to hold the entire section governed by the usual rule, and as ápplying only to the future.”
Certainly, there is no language in the act from which, it can be said that it was the intention of Congress to make it retroactive. On the contrary, its language indicates that it is prospective only. To give it a retrospective construction can only be brought about by supplying words or giving it an intendment which its whole purport does not justify, and which would bring about such unjust results that we are satisfied Congress did not intend any such consequences.
Other authorities supporting our .conclusion are: U. S. A., for Strait, v. Fidelity & Guaranty Co., 80 Vt. 84; Burton v. Frank Seifert Plastic Co., 61 S. E. 933; Davidson Bros. Marble Co. v. United States, 29 Sup. Ct. Rep. 324.
The judgment of the District Court is reversed and the cause remanded for further proceedings in harmony with the views expressed in .this opinion.
Judgment reversed.
Mr. Justice Musser and Mr. Justice Garrigues concur.