(CNN) The Department of Homeland Security, largely hollowed out over the last four years, is moving with urgency to staff agencies with people who had front row seats to the hardline immigration limits rolled out under former President Donald Trump, in order to rescind them.
The department -- the third largest in the US government -- was closely tied to Trump's immigration actions and will continue to play a critical role in the coming months and years as those policies are reversed. Over recent days, the department has started to hire staff with extensive backgrounds in immigrant rights, immigration law and refugee resettlement.
"It will have a substantial difference in the ability of the department to execute because people understand what's going on," said Peter Boogaard, communications director at FWD.us and a DHS official under President Barack Obama. "The Trump administration weaponized the immigration system for four years. There's a clear understanding for many of these folks going back in what's at stake here."
Ashley Tabaddor, for example, will serve at US Citizenship and Immigration Services as its top lawyer after nearly 16 years as an immigration judge and holding various positions at the Justice Department before that.
During the Trump administration, Tabaddor, in her capacity as the president of the immigration judges' union, was outspoken about the impact of Trump's policies -- like imposing case quotas, reversing rulings and curtailing judges' ability to exercise discretion in some cases -- on judges and immigrants.
President Joe Biden's administration has begun taking steps to shift the tone -- from restricting immigration to welcoming immigrants -- in its first few days. Shortly after taking office, Biden released a slew of immigration executive actions and orders, including reversing the travel ban on predominantly Muslim countries, halting border wall construction and placing a 100-day pause on deportations.
Over the weekend, White House officials previewed more actions on the horizon, including creating a family reunification task force, addressing legal immigration and outlining a holistic approach to regional migration.
If confirmed, Alejandro Mayorkas, Biden's pick for Homeland Security secretary, will be among those leading the charge. The Cuban-born Mayorkas was among Biden's earliest announced nominees and would be the first Latino and immigrant to serve at the helm of the department.
"The principles of homeland and security have been tremendously important in shaping my life. My father and mother brought me to this country to escape communism and to provide me with the security, opportunity and pride that American citizenship brings to each of us," Mayorkas told lawmakers last week, drawing on his own immigrant background.
The Senate Homeland Security Committee will vote on Mayorkas' nomination on Tuesday. If he receives approval from the committee and then the Senate, Mayorkas will be flanked with staffers well versed in the abundant policy changes of the last four years.
David Shahoulian, who worked at DHS under the Obama administration, is assistant secretary for border security and immigration. Shahoulian also served as Democratic chief counsel of the House Judiciary Committee -- one of the key committees that obtained documents from the Trump administration about the controversial "zero tolerance" policy that resulted in the separation of thousands of migrant families.
He's joined by Adam Hunter, who serves as deputy assistant secretary on immigration for DHS. Hunter comes from the Refugee Council USA, a coalition of 29 nongovernmental agencies focused on refugee protection. Biden has committed to raising the ceiling for how many refugees can come to the US after years of historic lows.
Angela Kelley, who has an extensive background in immigration policy, is joining as senior counselor on immigration.
Early on, the makeup of the Biden-Harris transition team reviewing DHS signaled the incoming administration's awareness of those actions, with Ur Jaddou, former chief counsel at US Citizenship and Immigration Services, as the team lead. Jaddou is rumored to be filling the role of director at that agency.
"The Biden immigration team is stocked with seasoned professionals who understand the nuances of immigration enforcement," said John Sandweg, who served at DHS under Obama.
Sharmistha Das, who worked for then-Sen. Kamala Harris, is the deputy general counsel for DHS. Her name has since appeared on a document delaying a Trump regulation that would bar asylum seekers from countries with disease outbreaks.
Other familiar names in immigration circles, like Tyler Moran and Esther Olavarria, have also come to fill top roles. Moran, who also served under Obama and as senior policy adviser to then-Senate Democratic leader Harry Reid of Nevada, is now special assistant to the President for immigration for the Domestic Policy Council and playing a critical role in the administration's immigration legislative push.
During the US Conference of Mayors winter meeting Saturday, Olavarria and Moran previewed upcoming immigration actions. Olavarria cited a future executive order that would rescind Trump proclamations that had largely barred the admission of low-income immigrants.
"These are policies that ignored the decades -- and centuries, actually -- of contributions that immigrants have made to our economy, to our society, to our culture," Olavarria said. "We'd rescind those policies and return to a country that welcomes immigrants and acknowledges their contributions."
Another executive action would present a new vision for migration, like providing funding to address root causes of migration and standing up a refugee admissions program for Central Americans, according to Olavarria, who also nodded to actions that would put in place a "fair but efficient asylum program" on the US-Mexico border and restore the US refugee admissions program.
Moran stressed, however, that while Biden can make inroads on immigration policy through executive authority, it's still necessary to pass legislation.
"The President does have a lot of authority to fix the immigration system in a number of different ways," Moran said. "But what really the President cannot do is provide permanent status to people, and we've made so many runs at this but we really have to get it done to make sure that people are on a path to citizenship."