Declaring the start of the "Trump era," Attorney General Jeff Sessions announced during a visit to the U.S.-Mexico border Tuesday that migrants deported from the U.S. who illegally re-enter the country will face felony charges and a stepped-up enforcement program.

"For those that continue to seek improper and illegal entry into this country, be forewarned: This is a new era. This is the Trump era. The lawlessness, the abdication of the duty to enforce our immigration laws, and the catch-and-release practices of old are over," Sessions said in his prepared remarks, addressing Customs and Border Protection personnel in Nogales, Arizona.

Federal attorneys must now "consider" bringing felony charges – which carry stiffer penalties than misdemeanor violations – against people caught re-crossing the border, and must more vigorously pursue felony prosecutions against people who help migrants illegally enter the U.S. and those who harbor them once they arrive, according to a two-page memo distributed to Justice Department attorneys.

Cases involving gangs, trafficking, assaults on law enforcement, as well as document and identity fraud, will be made particular priorities.

"Under the president's leadership and through his executive orders, we will secure this border and bring the full weight of both the immigration courts and federal criminal enforcement to combat this attack on our national security and sovereignty," Sessions said.

Neither the Justice Department nor the Department of Homeland Security, which oversees immigration enforcement, explained how exactly an increase in felony convictions might aid deportation efforts.

Notably, President Donald Trump's executive orders on immigration, signed Jan. 25, do not make a distinction between felonies and misdemeanors, instead declaring that anyone convicted of or even charged with a "criminal offense" is a priority for deportation.

However, a memo from Homeland Security Secretary John Kelly on implementing the president's orders suggests that anyone with a felony conviction can be considered a priority for removal.

The nation's top immigration officials, the document states, "may, as they determine appropriate, issue further guidance to allocate appropriate resources to prioritize enforcement activities ... for example, by prioritizing enforcement activities against removable aliens who are convicted felons or who are involved in gang activity or drug trafficking."

It's unclear whether the attorney general's directive will apply to people who are already in the country or instead will be used only for those caught at the border going forward.

The attorney general did make clear, however, that a primary goal is deterrence. He issued what are perhaps the Trump administration's strongest statements yet on immigration since the president was on the campaign trail, vowing to "take our stand against this filth" of criminal gangs and declaring the nation's southwest border "ground zero in this fight."

Enhancing the kinds of penalties that immigrants and those who help them may face, he said, will help deter people from even attempting to cross the border illegally – long before the president builds his promised border wall. Meanwhile, a surge of 50 immigration judges this year and another 75 next year – brought aboard through a "streamlined hiring plan" – will speed deportation proceedings and help prevent people from absconding before their next court dates.

"This is what happens when you have a president who understands the threat, who is not afraid to publicly identify the threat and stand up to it, and who makes clear to law enforcement that the leadership of their country finally has their back," Sessions said in his prepared remarks. "Together, we will drastically reduce the danger posed by criminal aliens, gang members and cartel henchmen."

Immigration advocacy and legal services groups, however, were quick to denounce the moves. The national American Immigration Lawyers Association said the Trump administration was "wasting more federal taxpayer dollars going after illegal border-crossers instead of protecting the American public."

"AG Sessions is pouring more resources into prosecuting people who cross the border illegally – most are seeking to join their families – rather than going after violent offenders and gun and drug smugglers who pose a real threat to Americans and our communities," says Gregory Chen, the group's director of government operations.

The Department of Homeland Security maintains it has seen a significant drop in the number of apprehensions at the U.S.-Mexico border since Election Day.

Last month, agents and officers along the border took 17,000 people into custody – a 71 percent decrease from the 58,478 people apprehended in December. Homeland Security Secretary John Kelly has attributed the drop to stepped-up immigration enforcement under Trump.

That decline corresponds with a broader trend stretching at least to 2006, and perhaps as early as 1996, with apprehensions falling by as much 93 percent in the past 20 years.