In 1996, McConnell signed a statement supporting a constitutional amendment to ban abortion, which read, "Abortion kills 1.5 million innocent human beings in America every year. ... We believe that the abortion license is a critical factor in America's virtue deficit."
As a respected constitutional scholar during his law school tenure, McConnell contended that originalism is consistent with the Supreme Court's 1954 desegregation decision Brown v. Board of Education, as opposed to critics of originalism who argue that they are inconsistent. He has likewise argued that the Court's decision in Bolling v. Sharpe was correct but should have been reached on other grounds, as Congress never "required that the schools of the District of Columbia be segregated."
McConnell was highly critical of the Supreme Court's decision in Bush v. Gore:
I imagine that Gov. Bush and his supporters will put on a brave face and defend this decision, but I cannot imagine that there is much joy in Austin tonight. The Supreme Court, with all the prestige of its position in American public life, could have brought closure to this matter. But instead, by straddling the fence, the court has produced a combination of holdings that can please no one.
McConnell expressed skepticism on First Amendment grounds about restrictions on religious exercise imposed during the COVID-19 pandemic.
In 2021, McConnell's argument that Trump could be tried by the Senate after he left office because the second impeachment occurred while he was in office was frequently cited in Senate debates and in the media.
While on the Tenth Circuit, McConnell wrote scores of judicial opinions. The Supreme Court reviewed four cases in which McConnell wrote an opinion; in each case, the Court reached the same result as McConnell. First, in Gonzales v. O Centro Espirita Beneficente Uniao do Vegetal (2006), a case involving the religious use of a hallucinogenic tea, the Supreme Court affirmed 8–0 a Tenth Circuit en banc decision to which Judge McConnell wrote a concurring opinion. Second, in Fernandez-Vargas v. Gonzales (2008), a case involving the retroactive application of a statutory provision limiting appeals from immigration removal orders, the Supreme Court affirmed 8–1 a Tenth Circuit panel decision written by Judge McConnell. Third, in Begay v. United States (2008), a case about whether a felony conviction for driving under the influence is a crime of violence for purposes of the Armed Career Criminal Act, the Supreme Court reversed 6–3 a Tenth Circuit panel decision from which McConnell dissented. Fourth, in Pleasant Grove City v. Summum (2009), a case involving whether the presence of a Ten Commandments monument on government property gave another religion a First Amendment right to place its own monument on the same property, the Supreme Court unanimously reversed a Tenth Circuit panel decision that McConnell had challenged by writing a dissent from the denial of rehearing en banc.
United States v. Patton (2006). Commerce Clause. Writing for the court, McConnell upheld a federal statute prohibiting the possession of body armor by felons. Even though the statute, as applied to Patton's intrastate and noncommercial possession of body armor, could not be sustained under any of the three Lopez categories the Supreme Court established, it fell within the Commerce Clause under another line of Supreme Court precedent (Scarborough) and noted the tension between the two sets of precedents. The court also rejected Patton's due process and necessity claims. The case was covered by Decision of the Day and The Volokh Conspiracy and was the subject of a constitutional law final exam at Cornell.
Testimony on constitutional term limits for Supreme Court justices
On June 30, 2021, McConnell provided testimony to the Presidential Commission on the Supreme Court of the United States on the dangers of increasing the Court's size. He proposed a constitutional amendment to address such dangers, including an 18-year term limit on justices and appointment of a justice in each odd year, unless the Senate voted against the appointment.
Highlights of his testimony include:
Any attempt to increase the size of the Court would be widely, and correctly, be regarded as a partisan interference with the independence of the Court.... It is no exaggeration to say that this would destroy one of the central features of our constitutional system, the independent judiciary.
This [McConnell’s] proposal, if adopted, would have several salutary effects. It would make the power of the president to name Supreme Court justices regular, fair, and consistent, and thus likely would lower the political stakes of each nomination. The political balance of the Court would reflect the opinions of the people over time as expressed in their choice of presidents and senators, rather than the happenstance of health or accident or the strategic timing of the justices.