Kennedy was a conservative justice who was surprisingly liberal on religion-related issues like LGBT rights and abortion policy.
Justice Anthony Kennedy spent three decades on the Supreme Court, playing a pivotal role in rulings that expanded LGBT rights, protected religion in the public square and ensured access to abortions.
But when it comes to his religious freedom legacy, he may be remembered most for the questions he never answered, according to legal experts.
In his opinions legalizing same-sex marriage and condemning anti-religion bias, Kennedy advocated for tolerating religious beliefs. However, his rulings rarely gave a clear picture of how to legislate tolerance through state and federal policies, said Thomas Berg, a professor of law and public policy at the University of St. Thomas.
Kennedy's rulings "are partly responsible for religious freedom being such a political hot potato," he said.
By retiring this year, Kennedy creates the possibility for a justice to join the Supreme Court who may be more willing to directly address public policy but less willing to work with liberal colleagues. Kennedy may come to regret not taking stronger positions when he had the chance, said Fred Gedicks, a law professor at Brigham Young University.
"It's almost as if he lost the courage of his convictions in the last few years," he said.
Kennedy was then-President Ronald Reagan's third choice for the Supreme Court when he was nominated in 1987. A Democrat-led Senate had rejected the Republican president's first choice, and the second nominee withdrew from the process after previous marijuana use came to light.
In general, Supreme Court nominees in the past weren't vetted as thoroughly as they are today, which meant presidents were sometimes surprised by their justices' future rulings, said Frank Colucci, an associate professor of political science at Purdue University Northwest. Throughout his time on the high court, Kennedy was traditionally conservative for the most part, but he often sided with liberal justices on cases involving LGBT rights, abortion restrictions and affirmative action.
"On some hot-button social issues, he cast the fifth vote for liberal outcomes," said Colucci, author of "Justice Kennedy's Jurisprudence: The Full and Necessary Meaning of Liberty."
In Planned Parenthood v. Casey in 1992, a case about Pennsylvania laws limiting access to abortion, Kennedy could have joined with his fellow conservative justices to overturn Roe v. Wade, the landmark 1973 ruling affirming a woman's right to an abortion. Instead, he supported liberal justices' effort to protect Roe's core and ensured abortion restrictions couldn't place an undue burden on women, said Helen Knowles, author of "The Tie Goes to Freedom: Justice Anthony M. Kennedy on Liberty."
"I don't think it's possible to exaggerate (Kennedy's) influence on abortion law in the last 30 years," she said.
Kennedy authored the majority opinion in a series of cases expanding legal protections for members of the LGBT community. He struck down laws preventing homosexuality from being a protected class and criminalizing same-sex relationships, and, in Obergefell v. Hodges, legalized same-sex marriage in 2015.
"Kennedy believes extremely strongly that the government should be treating everybody equally. It shouldn't be treating anybody different based on membership in a specific group or an individual trait," said Knowles, an associate professor at State University of New York at Oswego. "He talks a lot in his gay rights opinions about the importance of individual dignity."
These decisions angered many conservatives, including religious Americans who oppose abortion rights and believe marriage is properly reserved for unions between one man and one woman, Berg said.
"Religious conservatives were very upset by the Casey decision and then by Obergefell," he said. "Some people would say Kennedy attacked religious freedom just by recognizing same-sex marriage."
Record on religious freedom
On cases related to the First Amendment's religion-related protections or the federal Religious Freedom Restoration Act, Kennedy could also be surprising, according to legal experts.
He routinely pointed out and rejected animus against religion, but he also opposed the government imposing faith on the general public in cases that involved prayer at public school graduation ceremonies and school-sponsored sporting events.
"Justice Kennedy's overall religious freedom record is difficult to summarize because it's complex," said Melissa Rogers, a nonresident senior fellow in governance studies for Brookings Institution and co-author of "Religious Freedom and the Supreme Court," in an email.
In 1992, he joined the majority opinion in Employment Division v. Smith, which many observers viewed as a blow to religious freedom. The Supreme Court ruled it was lawful for government to restrict religious practice if the practice violated a law that applied to everyone.
Congress responded to the ruling by passing the Religious Freedom Restoration Act, which requires government to prove a compelling interest and show it is using the least restrictive means possible to enforce public policy that burdens someone's faith.
In the case City of Boerne v. Flores in 1997, Kennedy wrote the majority opinion stating that the Religious Freedom Restoration Act does not apply to state law. As a result, many conservative-dominated state legislatures passed strong protections for religious residents without regard for the LGBT community and blue states mostly ignored the concerns of people of faith, Berg said.
"We have a situation where, in many states, the dominant group will not give much protection to the other group," he said.
Kennedy did not oppose prayers before government meetings and religious displays on government property, but he wrote the Lee v. Weisman opinion in 1992 that found prayers at graduation ceremonies for public schools violated the First Amendment.
"Justice Kennedy was sensitive to state pressure on children to participate in religious practices," Rogers said.
He was also worried about government policies or behavior that unfairly targeted a faith group or individual believer. Kennedy called out government hostility toward religion in Church of the Lukumi Babalu Aye v. City of Hialeah, a case about whether a law banning animal sacrifice targeted members of the Santeria religion, and again in Masterpiece Cakeshop, Ltd. v. Colorado Civil Rights Commission, which involved a Christian baker who did not want to provide a wedding cake for a same-sex wedding.
"It was a pattern in Kennedy's opinions that he tended to protect rights by finding that the laws restricting those rights stemmed from animus or hostility," Berg said.
In Masterpiece Cakeshop, one of the highest profile cases of Kennedy's final term, two of Kennedy's core legal concerns came to a head. The case asked justices to consider if it was possible to protect religious objectors to same-sex marriage and members of the LGBT community at the same time.
"I was wondering what he was going to do in Masterpiece Cakeshop because that case was squarely at the intersection of two areas of law he cares deeply about: religious toleration and toleration of people regardless of their sexual orientation," Knowles said.
Instead of outlining what should happen when religious freedom protections conflict with LGBT nondiscrimination law, Kennedy and the six justices who joined his majority opinion focused on unlawful bias exhibited by members of the Colorado Civil Rights Commission. They called for respect for all Americans.
"These disputes must be resolved with tolerance, without undue disrespect to sincere religious beliefs and without subjecting gay persons to indignities when they seek goods and services in an open market," Kennedy wrote.
The Masterpiece Cakeshop ruling adds to Kennedy's reputation as someone who cares deeply about civility, Knowles said. He wanted the law to treat all people equally, and he tried to understand and empathize with competing viewpoints.
"I think he did a really good job of preserving his gay rights legacy and his legacy" of respect for diverse beliefs, Knowles said.
However, some legal experts worry that in Masterpiece Cakeshop and other cases Kennedy did not go far enough to turn calls for civility into legally binding precedents.
"He spoke about the importance of religious neutrality and respect in theory, but he never spelled out how far that would actually go in operation," Berg said.
For example, in the Obergefell ruling, Kennedy affirmed religious Americans' right to continue teaching that same-sex marriage is immoral. But he didn't explain what to do when these teachings lead to unlawful discrimination against gays and lesbians.
"He left open the question of how much religious colleges or faith-based adoption agencies could adhere to their (moral) rules in the face of anti-discrimination laws. He never made that clear," Berg said.
Kennedy also failed to take a stand for religious freedom in Trump v. Hawaii, the travel ban case, Gedicks said. In his concurring opinion, Kennedy wrote about why animus against a religion is wrong, but he was willing to overlook Trump's harsh criticisms of Islam.
"It seems odd to me that he knew he was going to retire and it was virtually the last case in which he was going to participate, and yet he didn't take the opportunity to further develop his animus theory," Gedicks said.
For Berg, Trump v. Hawaii encapsulates Kennedy's overall religious freedom record.
"He spoke about religious freedom in theory very strongly and eloquently, but that didn't always translate into broad protections in practice," he said.