In 2017 and 2019, Gregory T. Monahan, now the acting chief of the U.S. Park Police, contacted the U.S. attorney’s office in San Francisco and asked prosecutors to dismiss criminal cases against employees of the Bay Area’s Presidio Trust, including one count of assault on an officer, a new inspector general’s report finds. Both times, the prosecutors did drop the cases — once over the strong objection of a Park Police supervisor in San Francisco — but the agency has no rules or ethical guidelines to prohibit such intervention by police commanders, the Interior Department’s inspector general concluded.

A spokeswoman for the National Park Service, which oversees the Park Police, said Thursday that the lack of a policy on dismissing cases “is being corrected.” The vice chairman of the police officers union noted that Park Police general orders state that “an officer shall not interfere with the cases of another officer except by consent of such officer or that officer’s supervisor.” In both cases, the report found, Monahan did not speak to the arresting officers.

Monahan, 48, was promoted to acting chief last September and is under scrutiny for his actions during the Park Police’s operation to clear protesters out of the area around Lafayette Square before a visit by President Trump on June 1. Monahan and the Park Police spokesman did not respond to phone and email messages Thursday seeking comment.

The inspector general’s report does not propose any discipline or policy review but provided its findings to the deputy director of the National Park Service “for any actions deemed necessary.”

Alexandra M. Picavet, the acting chief spokeswoman for the park service, noted that the report “did not have any findings of misconduct in their investigations into the allegations of abuse of power.” Picavet added, “The report did identify a gap in USPP policy in there is no written policy or guideline on when it would be permitted for citations, or tickets, to be voided. That is being corrected.”

The investigation was sparked by a complaint last September from the then-chairman of the Park Police officers union, Michael E. Shalton Jr., who said Monahan’s actions were a “severe abuse of authority.” Shalton, now the vice chairman of the officers Fraternal Order of Police chapter, said the inspector general’s report was “watered down” and called for Monahan to resign.

“Interfering, tampering or fixing cases is against the law,” Shalton said, “and should be prosecuted, period. Considering Chief Monahan’s blatant disregard for law, rule, and regulation I believe it’s in his best interest to step down.” He said a recent FOP survey of Park Police rank-and-file members showed that officers have “no faith in his leadership.”

In addition to filing a complaint with the Office of Special Counsel, which was then investigated by Interior’s inspector general, Shalton also filed a complaint with Attorney General William P. Barr, asking for an investigation into interference with the criminal justice system. That complaint was rejected, said John V. Berry, an attorney representing the FOP.

The Presidio is a former military base that was turned over to the Park Service in 1994, and the Presidio Trust is a federal agency that manages the park and helps fund the Park Police in San Francisco. Shalton said that the Presidio’s chief executive, Jean Fraser, contacted Monahan directly to ask that the charges be dropped in both cases. The inspector general’s report does not name any of the participants publicly, even Monahan. But the details of the report align with Shalton’s complaint.

Fraser and her spokeswoman did not respond to email and phone messages Thursday.

Monahan, 48, has been with the Park Police since 1997, served as a patrol officer on the George Washington Memorial Parkway in the late 1990s and early 2000s, and began rising up the chain of command in 2007. By 2017, Monahan was a deputy chief in charge of the Park Police contingent in San Francisco, though he remained based in Washington.

In July 2017, four Presidio Trust employees were found at the property’s bowling alley with alcohol, which is prohibited on the property, and abusing bowling alley employees, Shalton’s complaints said. When Park Police officers arrived, the four employees continued to be belligerent, pushed one officer, and ultimately ended up with 10 criminal charges, including assault on an officer. The employees answered with a complaint of excessive force against the officers, which was ruled unfounded.

An administrative mix-up caused the charges to not be entered into the court system until early 2018. The inspector general report says an unnamed Presidio Trust official contacted Monahan asking him to dismiss the charges because it would create “an appearance of retaliation against the Trust employees.”

At Monahan’s direction, a Park Police manager sent an email to the U.S. attorney’s office in San Francisco in March 2018 requesting that the cases be dismissed. Shalton’s complaint says a Park Police major in San Francisco “was strongly opposed to dropping the criminal charges,” and the inspector general found that the arresting officer was not consulted. The prosecutor told the inspector general that when police request a dismissal, the prosecutors typically agree without further investigation.

In March 2019, an alarm alerted Park Police to two employees at the Presidio golf course after hours. The allegedly initially refused to provide identification and were charged with failure to obey lawful orders. Again, “the Presidio Trust official” complained to Monahan, the report states. Monahan told investigators that because one of the employees was wearing a shirt with the Presidio logo, the officer should have assumed the person was an employee, “thus obviating the need for the individual to produce government-issued identification.”

Monahan then asked one of the Park Police supervisors to have the cases dismissed, the report states, and the supervisor refused. “Do not ask me to have these tickets dismissed, I will not do it,” the supervisor said she told Monahan. “This is the second time this has happened. You need to let the courts run its course.” Instead, Monahan directly called prosecutors and had the cases dropped, the report states.

Monahan told the inspector general investigators he “believed that the USPP is subordinate to the Presidio Trust leadership.” The investigators then spoke to former Park Police Chief Robert MacLean and a park service executive who both said the Park Police are not subordinate to the Presidio Trust.

The inspector general’s report found that Monahan “had the discretion to request that the tickets be dismissed” and there was no Park Police general order or Interior Department policy on the issue, but Monahan “appeared to deviate from past USPP practices at the Presidio when requesting the dismissals.”

Shalton noted that General Order 32.03 not only prohibits interfering with another officer’s case, but also says “an officer shall perform the duty of a police officer fairly, impartially, and judiciously.”

Berry, the FOP’s lawyer, noted that the case was serious enough that the two top Park Police supervisors in San Francisco cooperated with Shalton’s complaint and the inspector general investigation of their boss.

“Everyone’s got to be treated equally, in today’s law enforcement age,” Berry said.