The Roberts Court, which began in 2005 and has been altered by two replacements — Sonia Sotomayor in 2009 and Elena Kagan in 2010 — has been asked to clarify the precise nature of the church-state relationship on several matters.

One topic the court addressed is whether religious symbols may be displayed on public property:

• In 2009, the court handed down a 9-0 decision in Pleasant Grove City v. Summum allowing a town in Utah to keep its display of the Ten Commandments in a public park. The case came before the court after the city rejected a monument proposed by members of the Summum religion who wanted to display their faith’s Seven Aphorisms in the park as well.
• In 2010, Kennedy wrote the opinion for the 5-justice majority in Salazar, et al., v. Buono, which upheld the constitutionality of the 6 ½-foot Mojave Memorial Cross in California on land maintained by the National Park Service.

One case dealt with the controversial issue of prayer before public meetings:

• In 2014, Justice Kennedy wrote the majority opinion in Town of Greece v. Galloway, in which the court defended, in a 5-4 decision, the right of the city to begin its meetings with sectarian prayers, of which all but 4 of its 127 monthly sessions between 1999 and 2010 were explicitly Christian.

The case came before the court after a Jew and an atheist from the New York town — uncomfortable with having to either feign piety or stand out in front of their fellow citizens and powerful board members during these prayers — were told to close their ears or wait in the hall until the invocation was over. Kennedy did not regard such prayers as “impermissible coercion” and expressed caution about the government deciding which kinds of prayer are appropriate in public venues.

The court likewise was asked to clarify whether taxpayer money could be given to explicitly religious causes:

• In 2007's Hein v. Freedom from Religion Foundation, the court rejected taxpayers’ standing in challenging the allocation of government funds to “faith-based” initiatives.
• Again in 2010, in Arizona Christian School Tuition Organization v. Winn, the court rejected the standing of taxpayers who challenged the constitutionality of a tax credit that allowed filers to divert up to $50 to tuition organizations — some of them religious — rather than forward that money to the state.
• Also in 2010, the Supreme Court ruled in a 5-4 decision authored by Justice Ginsburg that UC Hastings College of the Law was not required to extend official recognition to a Christian organization that denied gays from rising to leadership positions on religious grounds. The court defended the state university's stipulation that all officially recognized groups must adhere to an inclusive "all-comers" policy.

Over the next several years, the court heard two major cases pertaining to the ill-defined relationship between state power and religious institutions, or institutions run by religious people:

• In 2010, the court unanimously defended the right of a religious institution to fire one of its employees who believed she had been unfairly discriminated against. When a Lutheran school in Michigan asked teacher Cheryl Perich to resign after she missed a term of teaching due to illness, Perich sought protection under federal workplace discrimination laws.

The school successfully convinced the court in Hosanna-Tabor Evangelical Lutheran Church and School v. EEOC that because one-sixth of Perich's teaching schedule was devoted to religious instruction, she should be regarded as a religious figure equivalent to that of a full-time minister and that the government's reach therefore did not extend into the affairs of the school.

• In 2014, the Supreme Court ruled 5-4 in Burwell v. Hobby Lobby that for-profit institutions run by religious citizens would not be required to pay for contraceptives that they believe are responsible for the death of a fetus in accordance with the Religious Freedom Restoration Act (RFRA). The decision allows these institutions to seek an accommodation and to transfer the cost of these medications onto a third party such as the internal plan administrator or the insurance company — with or without a government subsidy.

In her dissent against the 5-justice majority, Justice Ginsburg expressed concern that the ruling would prompt other institutions to deny different types of health care coverage to their employees. Jehovah's Witnesses could deny coverage of blood transfusions or Christian Scientists could refuse to pay for vaccinations.

These decisions reveal a relatively consistent and persistent split among the nine justices. The majority often cites the country's religious and ecumenical history and culture as a basis for affirming the public display of religious symbols and speech. In the Town of Greece decision, for instance, Justice Kennedy defended the public acknowledgement of a "higher power," so long as the prayers do not "threaten damnation or preach conversion."

The minority, however, warns that members of the religious majority often benefit most from these decisions — sometimes at the expense of religious minorities — and that the law should apply equally to all. In the Hobby Lobby decision, Justice Ginsburg articulated the slipperiness of the accommodationist slope and the constitutionality of her preferred secular approach:

Approving some religious claims while deeming others unworthy of accommodation could be ‘perceived as favoring one religion over another,’ the very ‘risk the Establishment Clause was designed to preclude.’

Commentators speculate on why many of the court's decisions on matters of religion have a consistent 5-4 outcome.

One explanation for the split is the court's religious differences. Six justices — Roberts, Scalia, Alito, Thomas, Kennedy, and Sotomayor — are professed Catholics, while the three liberal justices — Breyer, Kagan, and Ginsburg — are Jewish. In many of these cases, the liberal Catholic Sotomayor joins her Jewish colleagues on the bench, with the swing voter Kennedy often siding with his co-religionists.

Jonathan Alter attributes the conservative Catholic bloc's outlook on religious cases to their upbringing, as these justices were raised in the interlude between the peek of anti-Catholic discrimination and the more accommodating reforms instituted after Vatican II and are thus uniquely insensitive to religious pluralism and tolerance.

statements about the "preferential treatment" that the Constitution gives to religion and the exceptional role of Christianity in American public life.

However, others point to more secular, ideological differences on the bench.

Many of the decisions on religious cases reflect the court's differing attitudes toward other First Amendment issues. For instance, the justices broke the same way in the 5-4 Citizens United case as they did in the Town of Greece and Hobby Lobby decisions.

The court's ideological conservatives, in their high estimation of personal and religious liberty, treat religious speech as free speech and religious institutions as largely independent of governmental authority.

The court's liberals, however, are more wary of government in any way endorsing religious speech or granting religious institutions exceptions that are not extended to secular institutions or those run by religious minorities.

Currently, it is the conservative majority that is primarily dictating the Supreme Court's decisions on religion.