For years, Grant T. Sullivan had his name attached to high-profile, high-stakes cases filed against Colorado and its public officials in challenges to the state’s election laws, gun safety policies and its non-discrimination directives.

At his formal swearing-in ceremony as a judge on the state’s Court of Appeals, Sullivan thanked the policymakers he formerly represented.

“I’m grateful for your public service, even if it means you occasionally were sued and had to call me,” he said on Friday.

Gov. Jared Polis appointed Sullivan to the 22-member Court of Appeals last year, and he has been on the court since January. The ceremony, known as an investiture, was intended to formally honor the appointment.

Sullivan joined the Colorado Attorney General’s Office in 2011 and worked under two Republican and one Democratic attorneys general. He was part of the office’s public officials unit, where he represented the governor, secretary of state, attorney general, treasurer and various state agencies.

As a lawyer, Sullivan appeared in court to defend the state against challenges to Colorado’s law on campaign spending limits, the “red flag” law governing firearm access for allegedly dangerous individuals, and the COVID-19 vaccine mandate for the University of Colorado’s medical campus.

Sullivan’s judgeship application listed multiple cases he worked on that made it to the U.S. Supreme Court, including Masterpiece Cakeshop v. Colorado Civil Rights Commission, in which the justices sided with a Christian baker who declined to make a wedding cake for a same-sex couple, and Colorado Department of State v. Baca, in which the court approved of state laws regulating “faithless electors” in presidential elections.

“During my transition, then-Secretary of State Wayne Williams said, ‘Phil, you need to look at this case because it could go all the way to the Supreme Court’,” recalled Attorney General Phil Weiser, who spoke at Sullivan’s investiture, about the faithless electors challenge.

When Colorado lost in the federal appeals court, Sullivan suggested Weiser argue the case before the Supreme Court. Weiser said he was interested in doing so, but others in his department “had some pause.” Ultimately, Weiser argued the case himself and prevailed.

“You would take on the most difficult cases. You didn’t just do that, but you did it with enthusiasm,” he said. “It’s so clear that you were always feeling grateful for the chance to work on these cases. That is precious and that is infectious.”

Sullivan’s appointment to the Court of Appeals occurred days before a trial judge issued her ruling in another unique case of Sullivan’s: representing Secretary of State Jena Griswold in a challenge to Donald Trump’s eligibility to appear on Colorado’s 2024 presidential primary ballot.

“We are not always perfect. I will certainly make mistakes and I’m grateful to the Colorado Supreme Court for telling me when I do,” said Sullivan. “But I will always do my best to earn the public’s trust.”

Sullivan was a clerk for former Court of Appeals Judge John R. Webb and former state Supreme Court Chief Justice Nathan B. Coats. In his judicial application, Sullivan listed his experience with Metro Volunteer Lawyers, providing pro bono services to litigants in family law cases. He also described the event that inspired him to enter government service: when his father, a part-time county counselor in rual Kansas, came out as gay during Sullivan’s childhood.

“He never gave a second thought to the raised eyebrows among his government colleagues. His bravery made the community more accepting and the local government more diverse,” Sullivan wrote.

Chief Judge Gilbert M. Román called Sullivan “genuinely one of the nicest people.” He mentioned an unusual experience Sullivan had after three months on the job, participating in the “Courts in the Community” program at Fort Lupton High School when a gun scare prompted a lockout on the campus.

Kara Veitch, Polis’ chief legal counsel, recalled her interaction with Sullivan as she walked with him out of the governor’s residence post-interview. He asked how she was doing and she gave a superficial answer, only for him to respond, “No, how are you doing?”

“In a moment when this is all about him, Judge Sullivan reached out,” Veitch said. “I was going through a really hard time. My daughter had been in the hospital. That kind of empathy that you bring … this is the type of human that we need in public service.”

With Sullivan’s appointment, Polis has selected half of the Court of Appeals’ membership in just five years. He will appoint a 12th member later this year, when Judge Anthony J. Navarro steps down. In addition to Sullivan, Polis selected Judges Sueanna P. Johnson and W. Eric Kuhn from the ranks of Weiser’s office.

Sullivan also gave a shout-out to his fiancée, Aubrey Elenis, the director of the Colorado Civil Rights Division who herself was involved in a major Supreme Court case out of Colorado last year — 303 Creative v. Elenis, which featured a challenge to the state’s non-discrimination law.

“Let me pause here and answer the question that I just know is gnawing at the judges in the room,” Sullivan added. “Aubrey and I appreciate all of the offers, but we already have someone to officiate the wedding.”