Jeh Johnson, who led the Department of Homeland Security (DHS) during President Obama's second term, advised undocumented immigrants they are not required to open the doors of their homes to immigration authorities unless agents produce a warrant signed by a judge.

"If someone from ICE ERO comes to someone's home — unless they have a warrant — that person is not required to admit them," Johnson said on "Face the Nation" Sunday, referring to the Enforcement and Removal Operations (ERO) branch of Immigration and Customs Enforcement (ICE) which is responsible for apprehending people the government seeks to deport.

ICE was slated to begin a new wave of roundups on Sunday targeting about 2,000 undocumented families with open deportation orders living in major U.S. cities. The operations were first publicly announced last month by President Trump, who postponed them for a few weeks.

To prepare for the raids — which have left many undocumented immigrants living in constant fear — advocacy groups and Democrats have mobilized to mount a high-profile campaign designed to inform people who could be targeted about their rights and other information, one of them being Johnson's advice.

Pro-immigrant organizations want to make sure people are not opening their doors to ICE agents who do not have a search and seizure warrant signed by a judge. When conducting roundups, ICE agents often produce an administration warrant — but attorneys say that by itself does not give them the right to enter private property to apprehend someone.

Johnson also noted that just because someone is apprehended, that does not mean the person is automatically deported without access to any legal recourse.

"They have a right to a lawyer and they should not be deported from this country unless there has been a final order of deportation by an immigration judge after the individuals had an opportunity to go through the appellate process and make whatever claims for asylum they have," he said.

In fact, he suggested that some of deportations of those who are apprehended by ICE during the looming sweeps will be delayed or stopped as attorneys file motions to reopen their cases in immigration court. He noted that judges often grant new hearings for those who were ordered deported without being present in the courtroom. Attorneys have said that many people miss court because of bureaucratic errors, like their notices to appear being sent late or to the wrong address.

"Very often if someone's ordered deported in absentia without being present in court they have a right to a rehearing," Johnson said. "And so it's important for people particularly today and over the next week to know exactly what their rights are."

Like Obama, when Johnson was at the helm of DHS, he came under fire from progressive and pro-immigrant activists for the millions of deportations during their administration, as well as for his handling of the 2014 surge of unaccompanied migrant children from Central America coming to the U.S.-Mexico border. He and other Obama-era officials have noted that many of those deported during those years had criminal convictions and were migrants who had recently crossed into the U.S. illegally.