VATICAN CITY — Pledging that clerical sexual abuse should “never happen again,” Pope Francis on Thursday issued a sweeping new law aimed at holding leadership more accountable while overhauling how the Roman Catholic Church deals with accusations of abuse and coverup.

The rules, a mix of common-sense requirements and more technical provisions, are the church’s first major step to formalize all stages of fielding and investigating abuse claims, a process that has previously been subject to improvisation.

When the rules come into force June 1, priests and nuns will be required for the first time to report abuse accusations to church authorities. Dioceses will be given a year to set up offices or other systems for receiving abuse complaints while offering protection for victims and whistleblowers. Perhaps most significantly, a new method will be used to investigate complaints of abuse or coverup against bishops and other higher-ups — an attempt to address one of the scandal-plagued church’s long-standing trouble spots.

“We must continue to learn from the bitter lessons of the past,” Francis wrote in the introduction to the edict.

The rules are Francis’s latest attempt to contend with an abuse crisis that has eroded the reputation of the church and his papacy. The Vatican document comes nearly three months after Francis hosted a landmark clerical abuse summit in Rome and pledged concrete action to address the scourge.

“This is a very strong signal,” said Archbishop Charles Scicluna of Malta, a Vatican official who has investigated abuse cases. “Nobody in the leadership is above the law.”

However, some church watchdogs say the new rules fall short because they keep the handling of cases in-house.

Zach Hiner, executive director of the Survivors Network of Those Abused by Priests, said the church erred in thinking it could eradicate abuse by changing the rules but still relying on “the very same church structures that have been receiving and routing abuse allegations for years.”

The rules also do not address the contentious question of how to punish clerics convicted of abuse or coverup in church trials.

The law is in place for a three-year trial run and could be changed after that, depending on how the new rules play out. It is unclear, for instance, how the church will safeguard whistleblowers and whether an institution known for protecting its own can alter a culture through legal changes.

Predictions among experts on Thursday ranged widely over which aspects of the law, if any, would be most transformative.

One major aspect, though, regards the policing of bishops — an issue that has long confounded the church. Bishops are answerable only to the pope, and for decades they have been able to escape rigid oversight.

The new provisions outline a way in which bishops can help police their own ranks, the first time such a system has been put in place.

The rules lean on a miniature, de facto hierarchy within regions. If a bishop is accused of abuse or coverup, a metropolitan bishop — the figure who heads the largest regional diocese — can begin looking into the case with the backing of the Holy See. The metropolitan bishop is supposed to work on a set timetable and deliver his findings to the Vatican.

But there are exceptions to this system. If a metropolitan bishop himself is accused, another bishop in the region is chosen to investigate, based on seniority. The Vatican also has the option to choose someone else entirely. In all cases, lay experts can be involved, though it is not a requirement.

The steps for handling complaints of abuse and coverup against bishops borrow heavily from a proposal made by Cardinal Blase Cupich of Chicago during February’s summit on abuse. Cupich is a close Francis ally.

In presenting his ideas, Cupich said that “this past year has taught us that the systematic failures in holding clerics of all rank responsible are due in large measure to flaws in the way we interact and communicate with each other in the college of bishops.”

The laws also require all priests and nuns to swiftly report allegations of abuse or coverup to religious authorities. Previously, there was nothing on paper mandating them to report, though some were compelled by their conscience.

Although the clerics aren’t explicitly required to report abuse allegations to police — a contentious issue within the church — the laws do state that church officials should comply with “any reporting obligations to the competent civil authorities.”

The guidelines cover cases of sexual abuse not only against minors, but also against vulnerable adults and seminarians who are abused by someone in power. Over the past year, the church has faced an onslaught of cases in which higher-ups have been implicated — a notable shift from earlier decades, when the focus was primarily on individual priests.

In the United States, former cardinal Theodore McCarrick was defrocked earlier this year after a church trial found him guilty of abuse. In Australia, Cardinal George Pell is appealing his criminal conviction for the sexual assault of two boys. In France, Cardinal Philippe Barbarin was convicted in March of failing to report abuse accusations, the first time a church higher-up has faced criminal punishment in such a case.

The guidelines released Thursday could provide a starting point for discussions among U.S. bishops, who are preparing for an assembly in June. At a prior meeting in November, those U.S. Catholic leaders were set to vote on measures that would improve the handling of abuse cases. But the Vatican, controversially, intervened to stop the vote.

In a statement Thursday, Cardinal Daniel DiNardo, president of the U.S. Conference of Catholic Bishops, said the United States already has a framework in place that involves zero tolerance, the use of lay experts and a stipulation for reporting abuse to civil authorities. U.S. Catholics, he said, are positioned “readily to bring the Holy Father’s instructions to action.”

DiNardo said national-level bishops’ conferences still have the “latitude” to enact their own measures.

“In publishing this new law, which is applicable to the Church throughout the world, Pope Francis has made clear that protection and healing must reach all of God’s children,” he said.