In April, protesters outside the nation's largest facility for unaccompanied migrant children noticed a familiar face enter the massive, fenced site in Homestead, Florida: former White House chief of staff John Kelly. Soon after, a local television station recorded footage of him riding on the back of a golf cart as he toured the grounds.

It wasn't clear why he was there, but Friday, Caliburn International confirmed to CBS News that Kelly had joined its board of directors. Caliburn is the parent company of Comprehensive Health Services, which operates Homestead and three other shelters for unaccompanied migrant children in Texas.

Prior to joining the Trump administration in January 2017, Kelly had been on the board of advisors of DC Capital Partners, an investment firm that now owns Caliburn.

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The Caliburn board includes other former high-ranking military personnel, including retired General Anthony C. Zinni, Admiral James G. Stavridis and Rear Admiral Kathleen Martin. The company's portfolio includes work in a variety of defense sectors.

John Kelly at a Trump rally in 2017. AFP/Getty Images

"With four decades of military and humanitarian leadership, in-depth understanding of international affairs and knowledge of current economic drivers around the world, General Kelly is a strong strategic addition to our team," said James Van Dusen, Caliburn's CEO. "Our board remains acutely focused on advising on the safety and welfare of unaccompanied minors who have been entrusted to our care and custody by the Department of Health and Human Services to address a very urgent need in caring for and helping to find appropriate sponsors for these unaccompanied minors."

Kelly joined DC Capital's board in February 2016 and stepped down in January 2017 when he was confirmed as Secretary of Homeland Security. Kelly switched jobs in July 2017 to become President Trump's chief of staff, a position he left at the end of 2018.

During Kelly's tenure, the administration pursued ambitious changes to immigration enforcement, and the average length of stay for an unaccompanied migrant child in U.S. custody skyrocketed.

In the past year, Comprehensive Health Services, the only private company operating shelters, became one of the most dominant players in the industry. Last August, it secured three licenses for facilities in Texas, totaling 500 beds, and in December, the Homestead facility began expanding from a capacity of 1,250 beds to 3,200.

Located on several acres of federal land adjacent to an Air Reserve Base, the facility is the nation's only site not subject to routine inspections by state child welfare experts.

Teens sleep in bunk-bed-lined dorm rooms, ranging in size from small rooms that fit 12 younger children to enormous halls shared by as many as 200 17-year-old boys, in rows of beds about shoulder-width apart.

During a tour in February, a program coordinator told CBS News that the older children prefer the cavernous digs. "They say it's like a slumber party," she said.

The days begin at 6 a.m. and follow a strict schedule, as children proceed in single-file lines from building to building, supervised by a staff of more than 2,300.

Under a federal court agreement known as the Flores settlement, unaccompanied migrant children are supposed to be housed in "non-secure" facilities, which means the children cannot be prevented from coming and going as they please. The facility's administrator said that is technically the case in Homestead, but acknowledged that the facility is surrounded by a tall covered fence and monitored by a large team of private security contractors.

The heavy security is one of a slew of issues repeatedly raised by lawyers tasked with monitoring compliance with Flores. They flagged Homestead, as well as a dozen other facilities, in a Dec. 31 letter to the Department of Justice outlining what they say are violations of the agreement.

Last October, Caliburn filed paperwork with regulators announcing an IPO, but cancelled those plans in March. On April 14, The Financial Times reported that DC Capital was instead seeking to sell 75 percent of the company. The company did not comment on the reported sale offer.

Federal contract records show Comprehensive received at least $222 million to operate Homestead between July 7, 2018 and April 20, 2019, and could receive much more — up to $341 million in payments between now and November for continued operation of the expanded site.

While Comprehensive and DC Capital appear to have reaped financial benefits through government contracts during and after Kelly's tenure as White House chief of staff, Richard Briffault, a Columbia Law School professor, said Kelly may not have broken any rules.

"It sounds like he's running between the raindrops. It doesn't sound great, but most likely he's not directly violating any policies," Briffault told CBS News. Briffault said government officials are barred from benefiting from their involvement in matters that involve specific parties, meaning that while serving at the White House, Kelly could not directly influence any decision to award a contract to a DC Capital company.

Delaney Marsco, ethics counsel at the nonprofit Campaign Legal Center, said her first question would be to ask whether Kelly ever consulted ethics officials about any involvement in formulating any policies surrounding unaccompanied minors.

"The fact is that when he was in the White House, the government took action that swelled the population of people that were in these facilities, and that benefited his former employer. That's the exact kind of situation that is why we have the ethics clause," Marsco said.

Now that he's left the White House, Kelly is barred from lobbying for five years, but is free to return to his old company. During that time, he cannot attempt to influence government policies that might benefit the company.

"This is classic revolving door," Briffault said. "Our system is designed in some ways to have that revolving door. We do assume, and we've been doing this for a long time, that (some public sector officials) are coming from the private sector, and that they'll eventually go back."