Police unions are one of the most important guardians of law enforcement in the United States — negotiating salary, benefits and most importantly protections for their members.

But that urge to protect also has another side in some cases — a resistance to reforms that they see as a potential threat to the safety of their officers or policing, especially in this time of great unrest.

From mandatory body cameras and reports anytime an officer has used their weapon to the expansion of civilian complaint boards, some union leaders have pushed back on proposed changes — for decades in some instances, according to Jack McDevitt, the director of Northeastern University’s Institute on Race and Justice.

“Some of the older unions, like ones in places like Boston and New York, have a lot invested in embracing the system that is in place,” he told ABC News.

Now, following the large-scale protests and calls for action following George Floyd’s death at the hands of Minneapolis police, some unions are expressing openness to change. The National Fraternal Order of Police, which has over 346,000 members, issued a statement this week in favor of Congress’s police reform legislation.

“When our citizens do not feel safe in the presence of police, that’s a problem—and the FOP intends to be part of the solution,” the union said in its statement.

While McDevitt and other experts say those groups cannot ultimately ignore the calls from the citizens they protect or the need to bring in new voices into their ranks, some are continuing to resist changes that they see as potentially injurious to their members.

They also remain deeply concerned about the crimes committed in cities around the country in conjunction with peaceful protests, including attacks on police officers.

This week, the unions representing several New York City police departments, such as the Police Benevolent Association, and other unions representing law enforcement in the state issued a letter condemning the state’s legislature for its newly passed police reform bills.

While the group acknowledged that “we share the universal desire for healing and positive change,” it decried the “push for passage of legislation and the adoption of policies that reflect only one perspective” without bringing unions to the table.

One of the measures being considered for repeal is Civil Rights Law 50-A, which blocked departments from disclosing records related to officer evaluations. Unions contended the release of the complaints would jeopardize officers’ reputations and safety.

“These types of claims are not reliable or fair indicators of an officer’s conduct, and would not be used to impugn any other person,” the unions said in the letter.

The Denver Police Protective Association, on the other hand, had a more subdued response to the protests and talked about the efforts it has taken over the years to reform their department, such as more training on cultural diversity and a ban on chokeholds.

“There is always room for conversation; there is always room for more improvement benefiting both the officer and the community,” the union said in a statement.

“I think some unions are seeing this an opportunity to step up and say how we can make policing better,” McDevitt said.

For the unions that are not endorsing reforms, the professor said those groups see these changes as hampering their power to protect their members’ working rights, particularly when it comes to collective bargaining agreements for their members.

“They think if there are collective bargaining changes, that they will lose their rights in negotiating salaries or other benefits for their officers if the reforms go through,” McDevitt said. “They come from a place where if management doesn’t want it, then they have to fight it.”

At the same time, some unions have used their power to put elected officials in the defensive. The group representing members of the Columbus Police Department, for instance, negotiated language in their 2017-2020 contract that limited the use of civilian complaints to a timetable as low as 60 days.

McDevitt added that the unions that are more open to the reforms acknowledge that these changes do come with data proven results that, ultimately, do protect officers.

“With body cameras, for example, a lot of time police officers have been reluctant to approve them,” he explained. “In more cases, the cameras tend to show allegations of police misconduct that were proven false.”

One problem that does need to be addressed in unions is diversity, according to McDevitt. The professor said this stems from a larger problem over the lack of diversity in police forces nationally, but it is critical that unions put more women and people of color in their leadership roles.

While the racial makeup of police largely mirrors the overall population, people of color are underrepresented in leadership roles, especially in smaller police departments, according to data from the Department of Justice.

New York police unions received criticism this week after a press conference denouncing proposed legislative action and decrying the treatment of their members in which many in attendance were white males.

Democratic Congresswoman Alexandria Ocasio-Cortez tweeted that the group “does not look representative of the NYPD at all,” tweeting a video of New York State Association of PBAs president Mike O’Meara speaking.

O’Meara, whose group represents unions in the New York City metropolitan area and elsewhere in New York State, spoke out against Floyd’s killing, but railed against the treatment of officers as a result.

PBA president Pat Lynch was also present at the press conference and denounced the “murder of an innocent person,” referring to Floyd. “That’s what happened. Let us be unequivocal.”

But he also took issue with legislators who “demonize” police officers “as if we’re the problem.”

The PBA did not immediately respond to a request for comment from ABC News.

“The union has to see if they don’t represent the community they won’t have legitimacy in negotiating table,” McDevitt said.

Scott Wolfe, an Associate Professor in the School of Criminal Justice at Michigan State University, said the response to police misconduct over the last few weeks have shown that police officers are showing more openness to accountability. Although unions may differ on their stance for reform, a majority have admitted that what happened to Floyd was wrong, which has been a departure from previous controversial police killings, according to Wolfe.

“There is virtually no disagreement that George Floyd was murdered and it can’t happen again,” he told ABC News.

Wolfe said that this common ground could be the place where police reform activists and unions can come together to achieve the same goal.

McDevitt, agreed, and said police unions can increase their bargaining power by taking public’s concerns seriously.

“Unions do not have a straight line of responsibility to the public. They answer to their members,” he said. “But when a strong aspect of the public says they’re not doing their job fairly, they have to listen.”

ABC News’ Luke Barr contributed to this report.