KAVANAUGH, Circuit Judge:
Plaintiffs received pension benefits from their service with the Metropolitan Police Department and salaries for their jobs with the Protective Services Division. But Section 5-723(e) of the D.C.Code requires the D.C. Government to reduce plaintiffs' salaries by the amount of their pensions. The goal of that statute is to prevent so-called double-dipping by D.C. government employees who retire and then are rehired back into another D.C. government job.
Pursuant to that statutory provision, D.C. reduced plaintiffs' salaries by the amount of their pensions. In response to their salary reduction, plaintiffs sued D.C. under a variety of theories. In an earlier round in this Court, we considered plaintiffs' claims under the federal Fair Labor Standards Act, the First Amendment, the Fifth Amendment, and the Equal Protection Clause. We ruled in favor of the plaintiffs on the Fair Labor Standards Act claim, ruled in favor of D.C. on the remaining constitutional claims, and remanded for further proceedings. See Cannon v. District of Columbia, 717 F.3d 200 (D.C.Cir. 2013).
Plaintiffs' victory on the FLSA claim gave them only partial relief and did not fully restore their salaries. On remand, still seeking to fully restore their salaries, plaintiffs therefore filed an amended complaint that asserted a new federal claim: that D.C.'s salary reduction provision violates the federal Public Salary Tax Act of 1939. See Pub.L. No. 76-32, § 4, 53 Stat. 574, 575 (1939) (codified as amended at 4 U.S.C. § 111(a)). The District Court rejected that argument, and so do we.
As relevant here, the Public Salary Tax Act allows States and D.C. to impose "taxation" on compensation paid to employees of the Federal Government, but only so long as the taxation does not discriminate against Federal employees as compared to state and local government employees, for example. 4 U.S.C. § 111(a).
Plaintiffs' argument under the Public Salary Tax Act has a plethora of potential problems. One initial (and in this case dispositive) problem with plaintiffs' novel theory is that the Act applies only to "taxation." And the D.C. salary reduction provision at issue here is not "taxation" of plaintiffs' pensions.
As a general matter, taxes are a "charge," usually "monetary, imposed by
Here, D.C.'s salary reduction provision is not a tax. It does not raise revenue. Rather, it operates on the opposite side of D.C.'s financial ledger. It reduces D.C.'s total expenditures on salaries. In particular, it decreases employees' salaries by the amount of their pensions from prior service in the D.C. government. Moreover, the reduction takes effect when the employee's salary is initially computed by the Protective Services Division. The salary reduction is thus not collected "through the normal means of taxation," which is yet another indication that this is not taxation for purposes of this Act. National Federation of Independent Business v. Sebelius, ___ U.S. ___, 132 S.Ct. 2566, 2596, 183 L.Ed.2d 450 (2012).
The salary reduction statute, in short, is nothing more than a way for D.C. to prevent so-called double-dipping and thereby reduce its expenditures on employee salaries. It is not a tax on plaintiffs' pensions. We therefore reject plaintiffs' novel Public Salary Tax Act argument.
In this second appeal, plaintiffs also renew the due process and takings claims that we found unavailing on their last trip to this Court. The law of the case doctrine bars us from reconsidering those holdings. See PNC Financial Services Group, Inc. v. Commissioner of IRS, 503 F.3d 119, 126 (D.C.Cir.2007).
Finally, plaintiffs contend that the District Court erred by declining to exercise jurisdiction over their separate D.C. law claims. (Plaintiffs' complaint tacked on several D.C. law claims to their numerous federal claims.) Plaintiffs primarily argue that D.C.Code § 1-815.02 gives federal courts "exclusive jurisdiction" over claims related to the payment of their pensions. But the salary reduction provision does not affect the amount or payment of plaintiffs' pensions. It affects only the amount of their salaries. See D.C.Code § 5-723(e) ("the salary of any annuitant ... shall be reduced by" the amount "of such annuitant's annuity") (emphasis added). Alternatively, plaintiffs contend that the District Court abused its discretion by declining to exercise supplemental jurisdiction over plaintiffs' D.C. law
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We affirm the judgment of the District Court.