President Donald Trump has nominated Neil Gorsuch to replace the late Justice Antonin Scalia on the U.S. Supreme Court.

Gorsuch is 49 years old and currently serves as a judge on the U.S. Court of Appeals for the 10th Circuit. He is a highly respected legal conservative whose credentials include a law degree from Harvard and a Supreme Court clerkship under Justices Byron White and Anthony Kennedy.

Gorsuch is perhaps best known for his sharp critique of the legal doctrine known as Chevron deference. Named after the Supreme Court's 1984 decision in Chevron U.S.A., Inc. v. Natural Resources Defense Council, Chevron deference says that when the federal courts are confronted with an "ambiguous" statute, the default position is for federal judges to defer to the statutory interpretation favored by the executive branch agency charged with enforcing that statute. "Federal judges—who have no constituency—have a duty to respect legitimate policy choices made by those who do," said Justice John Paul Stevens in his Chevron majority opinion. "While agencies are not directly accountable to the people, the Chief Executive is, and it is entirely appropriate for this political branch of the Government to make such policy choices." In other words, Chevron instructs the courts to tip the scales in favor of the executive branch in such cases.

But what about the judiciary's independent duty to act as "an impenetrable bulwark against every assumption of power in the legislative or executive," as James Madison once described the role of the courts? Doesn't Chevron deference amount to a judicial surrender in this core area of responsibility? Judge Gorsuch certainly thinks so. In his 2016 concurrence in Gutierrez-Brizuela v. Lynch, Gorsuch blasted Chevron deference as a "judge-made doctrine for the abdication of the judicial duty." According to Gorsuch, "under any conception of our separation of powers, I would have thought powerful and centralized authorities like today's administrative agencies would have warranted less deference from other branches, not more."

Gorsuch has also rejected pro-government deference in the Fourth Amendment context. For instance, in his 2016 dissent in United States v. Carloss, Gorsuch strongly objected to the majority's view that police officers had the "implied consent" to enter private property for a warrantless "knock and talk" on a homeowner's front porch even though the homeowner had placed multiple "No Trespassing" signs around the property and even on the front door. Under the government's flawed theory of the Fourth Amendment, Gorsuch complained, "a homeowner may post as many No Trespassing signs as she wishes. She might add a wall or a medieval-style moat, too. Maybe razor wire and battlements and mantraps besides. Even that isn't enough to revoke the state's right to enter." As Gorsuch dryly observed, "this line of reasoning seems to me difficult to reconcile with the Constitution of the founders' design."

Gorsuch demonstrated admirable and reassuring judgment in these cases. Not only did he cast a principled vote against overreaching law enforcement, he cast a principled vote against the overreaching executive branch. It's not difficult to imagine Gorsuch imposing the same severe judicial scrutiny against the misdeeds of the Trump administration.

On the hot-button issue of abortion, Gorsuch's judicial record is quiet. But in his 2006 book The Future of Assisted Suicide and Euthanasia, he did seemingly point in an anti-abortion direction, rejecting the case for legalizing assisted suicide on the grounds that "human life is fundamentally and inherently valuable, and the taking of human life by private persons is always wrong." Gorsuch also rejected the "libertarian case for assisted suicide" because, he argued, "faithful adherence to libertarian theory" would also justify the legalization of "mass suicide pacts…duels, and the sale of one's life (not to mention the use of now illegal drugs, prostitution, or the sale of one's organs)."

In that same book, Gorsuch also questioned whether the Supreme Court had any business protecting unenumerated constitutional rights—such as the right to privacy—under the Due Process Clause of the 14th Amendment, which says that no state may deprive any person of life, liberty, or property, without due process of law. Citing the work of conservative legal scholar Robert Bork, Gorsuch argued that the Due Process Clause is stretched "beyond recognition" when it is held to be "the repository of other substantive rights not expressly enumerated in the text of the Constitution or its amendments."

Unfortunately, Gorsuch's book did not address the meaning of another, closely related constitutional provision: the Privileges or Immunities Clause of the 14th Amendment. Regardless of what Gorsuch may think about substantive due process, the historical evidence clearly shows that the Privileges or Immunities Clause was originally understood to protect certain unenumerated rights. For example, according to Republican Congressman John Bingham of Ohio, the author of Section One of the 14th Amendment, among the "rights, privileges, and immunities" that the amendment secured against state infringement was "the right to work in an honest calling and contribute by your toil in some sort to the support of yourself, to the support of your fellowmen, and to be secure in the enjoyment of the fruits of your toil." In other words, interpreted according to its original meaning, the 14th Amendment does protect certain unenumerated rights, such as the right to economic liberty.

Given Judge Gorsuch's stated aversion to the judicial safeguarding of unenumerated rights via the Due Process Clause, it is essential to learn what he thinks about the judicial safeguarding of unenumerated rights via the Privileges or Immunities Clause. As Justice Clarence Thomas has rightfully observed, "the mere fact that the [Privileges or Immunities] Clause does not expressly list the rights it protects does not render it incapable of principled judicial application." The Senate Judiciary Committee should ask Gorsuch whether or not he agrees with Justice Thomas on this crucial matter of original meaning and constitutional law.

Now that President Trump has picked his nominee, the next move rests in the hands of the Senate Judiciary Committee. Will Senate Democrats seek to block Gorsuch's nomination, just as Senate Republicans recently blocked the nomination of Merrick Garland? Will the Republicans employ the so-called nuclear option and effectively end the filibuster for all Supreme Court nominees, just as the Democrats did in 2013 when they ended the filibuster for lower-court picks? Will the Gorsuch hearings be transformed into a referendum on the Trump administration itself?

One thing is certain: The battle over the future of the Supreme Court has just begun.