When President Trump announced that his new pick for labor secretary would be Alexander Acosta, a conservative law school dean with a deep background in public service, some career staffers at the Labor Department, Democrats and workers advocates breathed a sigh of relief.

The former U.S. attorney had served on the National Labor Relations Board, which made him familiar with labor laws and put him in stark contrast with Trump’s first choice: Andrew Puzder, a vocal fast-food chief executive who opposed substantially raising the minimum wage and rules that would expand eligibility for overtime pay.

But as Acosta’s Wednesday confirmation hearing approaches, some labor groups say questions remain about how much the more reserved dean — who “plays it close to the vest,” as one friend and colleague put it — will do to protect workers.

“Things were a lot clearer with Mr. Puzder,” said Kendall Fells, a national organizing director of the Fight for $15, a group that advocates for a higher minimum wage. “Workers have a list of questions they want to ask Mr. Acosta.”

Fells and other worker advocates say they want to know how Acosta, 48, would protect immigrant workers from deportation or retaliation, citing the Trump administration’s tough stance on immigration.

Others say they wonder whether Acosta would provide a voice for workers at a time when Republicans and business groups are trying to unravel some of the protections finalized under the Obama administration.

They want to know where Acosta stands, for example, on some of the Labor Department policies that have been in limbo since the election. Those include a rule that would expand the number of workers who qualify for overtime pay and a regulation that would require brokers working with retirement savers to put their clients’ interests first.

Sen. Elizabeth Warren (D-Mass.) said in a letter to Acosta this week that she’s concerned he “will simply fall in line with President Trump’s anti-worker statements and policies, which would be disastrous for the millions of American workers who rely on the Department of Labor’s enforcement of labor law.”

Warren, other Democrats and some consumer advocates say their concerns about his potential leadership style are illustrated in one of the issues he faced while heading the civil rights division of the Justice Department. An investigation from the Office of the Inspector General found that Acosta, who was the assistant attorney general of the division from 2003 to 2005, “did not take sufficient action” to supervise a former senior division official who was “inappropriately” hiring mostly conservative attorneys for the department.

“It took years for the civil rights division to be rebuilt and for it to return to its core focus of enforcing civil rights in an objective matter,” said Kristen Clarke, president of the Lawyers’ Committee for Civil Rights Under Law and an attorney at the civil rights division during Acosta’s tenure. “At the end of the day, this was all conduct that played out under Mr. Acosta’s watch.”

Acosta did not respond to requests for comment in time for publication.

But some friends and colleagues in his home town of Miami say that while Acosta is a private person, he is a fair leader who respects others’ views, even when they are different from his own. Ediberto Roman, one of the founding faculty members of the law school at Florida International University where Acosta is the dean, said Acosta has always been supportive of his work advocating for the rights of minorities, including undocumented immigrants. Roman said that in speeches and events, Acosta is more likely to emphasize the accomplishments of his students and colleagues than he is to tout his own work.

“He’s a straight-laced, honest guy who will do everything he can to do right by people,” he said.

Acosta advocated for the civil rights of Muslim Americans several times throughout his time at the civil rights division and at the law school. In 2004, for instance, he intervened with the Justice Department to help defend an 11-year-old girl in Oklahoma who was suing her school district for requiring her to remove her hijab on the grounds that it violated the school’s dress code. The school district settled with the Justice Department and adjusted its dress code.

Acosta, who is Cuban American, would fill one of the last major openings for Trump’s Cabinet and would be the only Hispanic member, if confirmed. The Labor Department has lacked a top leader for two months in part because of Puzder’s multiple hearing delays and his eventual withdrawal from the running after he lost of the support of several Republicans who were concerned about his record, including the revelation that he once hired an undocumented worker in his home.

After earning his undergraduate and law degrees from Harvard, Acosta established his career in Washington by working as an associate at the law firm Kirkland & Ellis and as an adjunct professor for George Mason University’s law school. Acosta also clerked for Supreme Court Justice Samuel A. Alito Jr., back when Alito was a judge on the U.S. Court of Appeals for the 3rd Circuit.

He returned to Miami in 2005 as a U.S. attorney for the Southern District of Florida and led several high-profile cases, including the fraud and conspiracy charges against Republican lobbyist Jack Abramoff, the prosecution of accused terrorist Jose Padilla and the case against Colombian drug cartel members Miguel and Gilberto Rodriguez Orejuela. In 2009 he joined the law school.

Acosta became the chairman of the board of directors for U.S. Century Bank, a Hispanic-owned community bank based in South Florida, in 2013. The bank was struggling then with mortgage loans that soured after the Great Recession, but Acosta helped turn the bank around by securing a capitalization deal that helped the bank stay in business and remain an independent community bank, said Ken Thomas a bank consultant in South Florida.

“You’ve got a good person, who is smart … listens to the pros and cons and then makes a decision,” Thomas said.

Read more:

Trump administration calls the structure of the Consumer Financial Protection Bureau unconstitutional in filing

In his first budget, Trump to struggling seniors: You’ll be on your own

Why the Fed rate hike won’t help savers any time soon