On July 15, 2026, former Iowa Attorney General Thomas J. Miller filed an amicus brief supporting Colorado in the en banc proceedings before the U.S. Court of Appeals for the Tenth Circuit in National Association of Industrial Bankers, et al. v. Weiser. Unlike the other amicus briefs filed in support of Colorado, Miller’s submission is unique because it is based not on academic research, economic analysis, or general principles of statutory interpretation, but on his personal experience administering Iowa’s consumer credit laws from the time the Depository Institutions Deregulation and Monetary Control Act of 1980 (“DIDMCA”) was enacted in 1980 through more than four decades thereafter.

Miller served as Iowa Attorney General from 1979 until 2022 (except for a four-year interruption from 1991 to 1995). He notes that he was Iowa’s Attorney General when Congress enacted DIDMCA and when Iowa immediately exercised its statutory right to opt out of DIDMCA’s interest-rate exportation provision. Because Iowa is the only state that opted out immediately after DIDMCA’s enactment and has remained opted out continuously ever since, Miller contends that he possesses unique firsthand knowledge regarding how Section 525 of DIDMCA has been understood and enforced since its adoption. He argues that the plaintiffs’ interpretation of the statute conflicts with Iowa’s longstanding understanding and application of DIDMCA’s opt-out provision.

Iowa’s Experience Allegedly Provides Contemporaneous Evidence of Congress’s Intent

Miller begins by arguing that the Tenth Circuit need not resort to extrinsic evidence because he asserts that Section 525’s text is unambiguous. In his view, the panel majority correctly concluded that when Congress authorized states to opt out of DIDMCA “with respect to loans made in such State,” it meant loans made to consumers in the opt-out state. He nevertheless argues that, if the en banc court concludes the statute is ambiguous, Iowa’s contemporaneous interpretation deserves substantial weight under the Supreme Court’s recent decision in Loper Bright Enterprises v. Raimondo, which recognized that longstanding governmental interpretations may inform a court’s understanding of ambiguous statutes.

According to Miller, Iowa’s experience is especially significant because it is the only jurisdiction that has continuously exercised its opt-out authority from the moment DIDMCA became law.

Miller Asserts That Iowa Believed Its Opt-Out Applied to Out-of-State State Banks

The brief traces Iowa’s historical regulation of usury.

Before Marquette National Bank v. First of Omaha Service Corp., Iowa regulated interest charged to Iowa borrowers regardless of where the lender was located. Although Marquette held that the National Bank Act preempted Iowa’s usury laws as applied to national banks, Miller notes that Iowa officials immediately recognized that the decision did not affect lending by state-chartered banks. Shortly after Marquette, the Iowa Attorney General issued an opinion concluding that while national banks could export their home-state interest rates, “if the lender institution is other than a national bank, Iowa law would control.”

When Congress enacted DIDMCA in 1980, Miller explains, it extended interest-rate exportation rights to state-chartered banks but simultaneously created an important safeguard absent from the National Bank Act by allowing states to opt out of the new preemption. Iowa exercised that right immediately, declaring that DIDMCA would not apply “with respect to loans … made in this state.”

Iowa Consistently Enforced Its Usury Laws Against Out-of-State State Banks

According to Miller, there was never any doubt within Iowa government that the state’s DIDMCA opt-out restored Iowa’s authority to enforce its consumer credit laws against loans made by out-of-state state-chartered banks to Iowa residents.

The brief points to a 1986 opinion issued by the Iowa Consumer Credit Code Administrator rejecting a New York state-chartered bank’s contention that Iowa’s opt-out did not apply to loans made by out-of-state banks. The Administrator concluded that Iowa retained authority to apply its consumer credit laws to loans made to Iowa borrowers despite the lender’s out-of-state location.

Miller further notes that Iowa has consistently enforced that interpretation in practice. While many out-of-state state banks voluntarily complied with Iowa law, the State also brought enforcement actions when lenders exceeded Iowa’s usury limits. According to Miller, these actions reflect Iowa’s uninterrupted position that its opt-out restored full authority to regulate loans made to Iowa residents by out-of-state state-chartered banks.

Miller Contends That Iowa’s Longstanding Position Supports Colorado’s Interpretation

Miller concludes that Iowa’s uninterrupted forty-six-year history of interpreting and enforcing DIDMCA strongly supports Colorado’s position.

While contending that the statutory text alone warrants reversal of the district court’s preliminary injunction, he argues that Iowa’s continuous interpretation since 1980 provides confirmation that Congress intended Section 525 to permit states to apply their usury laws to loans made to consumers within opt-out states, including loans originated by out-of-state state-chartered banks.

Observations

Former Attorney General Miller’s amicus brief is unlike the other filings in this case because it rests primarily on Iowa’s historical interpretation and enforcement of Section 525 of DIDMCA over the past forty-six years. According to the brief, because Iowa opted out immediately after DIDMCA’s enactment and has remained an opt-out state ever since, Iowa’s longstanding interpretation of the statute should inform the Tenth Circuit’s construction of Section 525.

That argument is open to serious question. The issue before the court is the interpretation of a federal statute enacted by Congress. Iowa cannot determine the meaning of federal law. As the Supreme Court made clear more than two centuries ago, “it is emphatically the province and duty of the judicial department to say what the law is.” Marbury v. Madison, 5 U.S. (1 Cranch) 137, 177 (1803).

Nor does the Supreme Court’s recent decision in Loper Bright Enterprises v. Raimondo, 603 U.S. 369 (2024), upon which Mr. Miller relies, support the proposition that a federal court should give special weight to a former state attorney general’s interpretation of a federal statute. To the contrary, Loper Bright reaffirmed that courts must exercise their own independent judgment in determining the meaning of federal statutes. If federal courts no longer give Chevron deference to the statutory interpretations of federal agencies merely because they administer a statute, it is even more difficult to see why they should defer to the views of a former state official who possesses no congressionally delegated authority to interpret federal law.

Indeed, the premise of the brief raises an obvious question. If Iowa’s historical interpretation is entitled to persuasive weight because it has remained an opt-out state since 1980, why should that experience be accorded greater significance than that of the overwhelming majority of states that either never exercised DIDMCA’s opt-out authority or subsequently repealed their opt-out statutes? The brief offers no principled basis for concluding that the experience of one state more accurately reflects congressional intent than the collective experience of the many other states.

Most significantly, Congress has assigned responsibility for administering and interpreting Sections 521 and 525 of DIDMCA to the Federal Deposit Insurance Corporation. Unlike a former state attorney general, the FDIC is the federal banking agency charged with implementing and interpreting the statute. In this litigation, the FDIC has filed an amicus brief with the en banc Tenth Circuit supporting the plaintiffs’ interpretation of Section 525. Whether or not the court ultimately agrees with the FDIC’s position, its views at least emanate from the federal regulator entrusted by Congress with administering DIDMCA rather than from a state official interpreting a federal statute outside the scope of any delegated federal authority.

Ultimately, Mr. Miller’s brief is best understood as an account of Iowa’s own regulatory history rather than an authoritative or persuasive exposition of federal law. Iowa’s enforcement practices may illustrate how one state has viewed its opt-out legislation over the past four decades, but it cannot answer the question before the Tenth Circuit: what Congress intended when it enacted Section 525 of DIDMCA in 1980. That question, as Marbury and Loper Bright make clear, is one for the federal courts to decide through their independent interpretation of the statutory text.