But the Trump administration also emphasizes that it is leaving intact the DACA program -- President Barack Obama's protections for so-called DREAMers -- even if the new rules chip away at protections for undocumented migrants overall.
The fundamental shift in US policy will likely continue to provoke fear in immigrant communities of a vast expansion of the government's use of its enforcement powers to potentially deport undocumented immigrants who have lived in their communities for years, and may have family members who are legal US residents or citizens.
DHS officials say the policies mostly enforce existing law and won't lead to an immediate massive round-ups of undocumented immigrants.
"We're not going to start changing this today, it's not going to start happening tomorrow," the official said of an expansion of who is eligible for expedited deportation. "You will not see folks rounded up or anything of the sort."
The memos, which were obtained
and reported on by CNN over the weekend, serve to expand upon the orders, which are unrelated to the controversial travel ban currently tied up in the courts and being re-written by the White House.
The guidance explains how the administration plans to put in place the goals dictated in Trump's executive orders, including vastly increasing the resources to Immigration and Customs Enforcement, Customs and Border Protection, building a wall along the southern border and taking a hard-line position on undocumented immigrants.
DHS officials repeatedly tried to emphasize that the policies are not an expansion of existing law.
"We're just simply trying to execute what Congress and the President has asked us to do," an official said. "We're going to do so professionally (and) humanely ... but we are going to execute the laws of the United States."
Language was included explicitly saying Obama's executive orders protecting young undocumented immigrants brought to the US as children and undocumented parents of US citizens would be an exception to a mandate that "the Department no longer will exempt classes or categories of removable aliens from potential enforcement."
A DHS official briefing reporters on the orders made note from the top that the policies would not be affected.
"No. 1: None of this affects DACA. No. 2, none of this affects DAPA/expanded DACA," the official said, adding that the latter policy is currently being blocked by the courts either way.
The guidance is still unclear in many respects. It rescinds Obama executive orders besides the deferred action for children and parents of citizens -- but notes that only "to the extent of the conflict" with new guidance, meaning some policies will remain in place.
For example, a fact sheet released by the department says that rules keeping churches and schools as off-limits from enforcement actions remain in operation.
Asked about the confusion over which policies do and do not remain in place, an official said, "There are a lot of internal policies and memoranda and procedures that have to be worked out individually and analyzed by the legal departments. ... That's a very deliberate project that will be conducted."
But the official emphasized the "sensitive locations" policy remains in place, and a second official said the rescinding of previous guidance largely applies for now to policy about prosecutorial discretion.
Through the memos, Kelly expands the government's immigration enforcement by instructing agencies to implement unused parts of existing law and by clarifying standards for certain protections, which add up to having sweeping implications for the processing of undocumented immigrants in the US.
While DHS officials stressed that the agency will use its limited resources to target "criminals," as Trump has said, they also acknowledged that people who were not targeted for deportation under Obama could be eligible in this administration -- giving broad latitude to agents in the field and regional offices to make decisions.
"The fact that you are not a priority does not exempt you from potential enforcement," an official said, adding that people with crimes like DUIs and status violations, or noncriminal histories but a final order of removal could be subject to deportation.
The Trump administration has set new enforcement priorities that could apply to virtually every undocumented immigrant in the US -- whereas the Obama administration had focused on serious and violent criminals -- sending fear through immigrant communities about indiscriminate arrests. Stepped-up ICE enforcement earlier this month, which netted nearly 700 arrests nationwide, only amplified fears. While similar enforcement actions were conducted under the Obama administration, anecdotes spread of nonthreatening undocumented immigrants being caught up amplified fears.
The memos reinforce giving broad leeway to immigration officers to make immediate decisions about whom to arrest and says officers should begin actions against individuals they meet in the course of their official duties.
The goal is to free immigration officers and law enforcement to make decisions, after critics of Obama's policies described them as having their hands tied.
But the administration also explicitly reserves the right to expand and prioritize targets, such as "against removable aliens who are convicted felons or who are involved in gang activity or drug trafficking."
Changes to use of laws
The new plan vastly grows the number of individuals who can be deported using "expedited removal" procedures, which affords immigrants almost no court proceedings.
Under the new policy, if someone can't prove he or she has been living in the US continuously for two years, he or she could now be eligible for expedited removal. Previously, this was limited in practice to people apprehended within 100 miles of the border and who had arrived within the past two weeks.
The memos also make a series of changes as part of ending so-called "catch and release," where undocumented immigrants awaiting court proceedings are granted parole and leave to enter the country pending court dates that can be years in the future.
It places stricter limits on who can be paroled instead of detained, making detention pending court proceedings the default for thousands of immigrants. In an attempt to deal with the potential strain on limited detention resources, Kelly orders a surge in immigration judges and facilities.
More difficult for asylum seekers
Along these lines, the guidance also makes it more difficult to receive asylum protections, a key exception to "expedited removal" that often lets people stay in the US as they await a final ruling on their eligibility for asylum.
Without explicitly changing the standard for "credible fear" -- the threshold at which asylum seekers are granted permission to continue to pursue court hearings on their asylum claim -- the guidance makes clear that asylum officers can use more discretion in determining an individual's credibility, and use their own knowledge to weigh against what migrants claim about potential persecution or torture back home.
Another change: Once people reach the credible fear point, instead of waiting for their full hearings on asylum in the US, the new guidance makes use of a law that allows non-Mexican migrants to be sent to Mexico to wait, provided they arrived through Mexico. The change could send potentially tens of thousands of non-Mexican migrants back over the border, and would largely apply to Central Americans who flee violence, gangs and drug cartels to seek refuge in the US.
DHS will also explore a video conference system to potentially keep these individuals in Mexico even for their court hearing, which could be conducted remotely.
In further tightening of protections that allow more leniency to certain immigrants, the administration is also looking to limit protections for unaccompanied minors that seek to enter the US.
The executive order notes that in some cases, individuals continued to receive protection as unaccompanied alien children even when they had a parent or guardian living illegally in the US, saying it led to "abuses" of the system.
Kelly's memo calls for new guidance to end those "abuses" -- which could restrict the eligibility that was previously given to all minors under 18 who arrived without a parent or guardian in the US able to care for them.