Almost 2,000 children were separated from their families over a six-week period in April and May.
"We do have a policy of prosecuting adults who flout our laws to come here illegally instead of waiting their turn, claiming asylum at ports of entry".
More than 2,000 children have been separated from their parents at border crossings and placed in detention centers, according to the Department of Homeland Security.
On her Monday night show, Fox News host Laura Ingraham quizzed Sessions about his "zero tolerance" immigration policy, which has been compared by former CIA Director Michael Hayden and Senator Dianne Feinstein (D-California) to the tactics used by Nazi Germany.
Although President Donald Trump and several members of his administration, including Homeland Security Secretary Kirstjen Nielsen, have repeatedly claimed the family separation policy must be enforced, legal experts, including this group of attorneys, have challenged such an assertion.
Last week, Nielsen visited Israel, toured its border barrier with Egypt and received a briefing on Israeli border technology to take away lessons for the US-Mexico border.
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Sessions said the issue was "whether we want to be a country of laws or whether we want to be a country without borders".
The emotional toll for migrant children caught at the border is not new.
USA officials have argued that the children are well cared for and that the government has high standards for the detention centers where they are being housed.
A Department of Justice bulletin from April 8 said those entering the country illegally would be met with "the full prosecutorial powers" of the DOJ.
"When we ignore our laws at the border we obviously encourage hundreds of thousands of people a year to likewise ignore our laws and illegally enter our country, creating an enormous burden on our law enforcement, our schools, our hospitals, and social programs", he said.
"The stories from the border make me ill". "Illegal entry is a crime as determined by Congress".
The stepped-up criticism comes after the department's internal watchdog released a report last week that criticized the FBI's handling of the 2016 probe into Hillary Clinton's emails but said political bias didn't affect the outcome of the investigation that eventually cleared her.