NEW YORK – Parents upset by the admission policy at a parochial school. Clergy and parishioners at odds over use of their building. A priest resisting a transfer to another parish.

It was once assumed that disagreements like these in the Roman Catholic Church would end one way: with the highest ranking cleric getting the last word.

But that outcome is no longer a given, as Catholics, emboldened after the clergy abuse scandals that erupted a decade ago this month, have sought another avenue of redress.

In recent years, clergy and lay people in the United States have increasingly turned to the church’s internal legal system to challenge a bishop’s or pastor’s decision about even the most workaday issues in Catholic life, according to canon lawyers in academia, dioceses and in private practice. Sometimes, the challengers even win.

In one example cited by veteran canon lawyers, parishioners wanted to bar musical performances in their church that weren’t liturgical. Their priest had been renting space to a local band. Regarding bishops’ often contentious decisions to close parishes, the liberal reform group FutureChurch posts a guide on its website called “Canonical Appeals for Dummies” on seeking Vatican intervention to stay open.

The reasons for the uptick are complex and reach back decades, involving changes in the church and broader society. Canon lawyers say the American concern for individual freedoms likely has played a role. So has the explosion of information on the Internet. But the change is also an unexpected consequence of the clergy molestation crisis, with the scandal exerting an influence far beyond cases that directly involve abusers.

“The focus on canon law and penal procedures in the case of sexual misconduct has made people aware that the church has a law system, it can work and people can take advantage of it,” said Michael Ritty, founder of Canon Law Professionals, a private practice in Feura Bush, N.Y. “For so long, especially in the United States, many of the lay people did not speak up and did not know how to speak up, and many people in the hierarchy did not know how to accept things when people did speak up. I think that is changing.”

No one knows the exact number of formal petitions before tribunals or agencies at the Vatican, or before church officials in the U.S. or in any country. The cases are guarded by pontifical secrecy, which bars advocates, judges and other parties from revealing details of the proceedings.

Still, U.S. canon lawyers say they have seen more widespread use of church law to resolve disputes.

Edward Peters, a canon lawyer and professor at Sacred Heart Major Seminary in Detroit, said the increase in canonical litigation is “indisputable.”

The Canon Law Society of America, a professional group for church lawyers, held a workshop on the trend called “Hierarchical Recourse: Can’t We All Just Get Along?”

Ritty founded his private practice in 2000 to keep active after he retired and now employs three other canon lawyers. Abuse cases are a significant part of his work, along with marriage annulments, but Ritty also has many cases relating to everyday church issues, such as use of money.

“Most of us, when we were training, were preparing for marriage tribunals, marriage annulments,” said Monsignor Patrick Lagges of Chicago, a canon lawyer for three decades who helped lead the canon law society workshop last year. “Now there’s such a broad range of things.”

Until recently, the only canon law most American Catholics knew related to annulments, church declarations that a marriage was never valid. The first complete code of canon law, published in 1917, was also the first to be translated from the Latin into English. Even then, the system was considered the province of an educated clergy-elite who were fluent in Latin and could quote directly from centuries-old papal decrees.

The Second Vatican Council, the 1960s meetings that ushered in modernizing reforms, aimed to make canon law more accessible. A revised legal code was eventually issued in 1983 by Pope John Paul II that placed new emphasis on the rights and obligations of all Catholics, lay and clergy. “The Christian faithful can legitimately vindicate and defend the rights which they possess in the Church in the competent ecclesiastical forum according to the norm of law,” canon 221:1 says.

Yet, no flurry of canonical petitions followed.

A few prominent cases played out in public. The ex-wife of former Massachusetts Rep. Joseph P. Kennedy II, son of Robert F. Kennedy, wrote a book about her appeal to reverse the church decision to annul their marriage of a dozen years. The Vatican took about a decade to decide the case, but ruled in her favor.

In the 1990s, some parishioners appealed Cardinal Joseph Bernardin’s decision to close their Chicago church. They succeeded in a phase of the appeal, but the building was ultimately shut down. Still, the numbers of cases remained small.

Then, 10 years ago, a crisis unfolded that became the worst in U.S. church history.

The Boston Globe persuaded a judge to unseal documents that showed the Archdiocese of Boston kept clergy who had molested children in parishes without warning parents or police. The outrage the news reports generated spread nationwide.

Soon, every American bishop was pressured to disclose diocesan records on abusive clergy. In June 2002, beleaguered church leaders gathered in Dallas, trailed by more than 750 reporters, to adopt a new child protection policy and discipline plan for guilty priests.

Suddenly, canon law was front-page news.

In many cases, the church’s internal legal system was the only recourse for church officials who wanted to remove clergy from public ministry or the priesthood. Most victims came forward decades after they had been molested, long after the statute of limitations for criminal prosecution.

So over several months, American bishops began a closely watched negotiation with Vatican officials over how they could change church law to streamline the removal of guilty priests. Canonical due-process rights for clergy emerged as a key issue.

Bishops spent hundreds of millions of dollars on child protection programs and more on settlements with victims.

But the damage was done. Trust in the bishops’ judgment plummeted. So, when bishops in some dioceses announced the next round of parish closures, part of a consolidation that started years ago, angry parishioners didn’t only protest and pray. They also hired canon lawyers.

Peters said petitions challenging decisions by bishops and other church officials have grown from a “tiny” to a “small” share of the church’s canonical actions. Still, the increase comes as bishops struggle to reassert their authority as teachers and leaders.

“A lot of times you’re delivering messages that maybe the bishops doesn’t want to hear,” Lagges said. “You have to go in and tell the bishop, ‘You can’t do this.’ Bishops don’t like to hear that.”