How Trump's policies are changing immigration enforcement in the US What you need to know about the new plans under Trump.

 -- Just after taking office, President Donald Trump issued two executive orders that called for a huge shift in enforcement priorities and the hiring of thousands of federal immigration officers — striking fear among many immigrants that the administration will amass a deportation force.

On Tuesday, Department of Homeland Security Secretary John Kelly issued two memorandums detailing how the DHS, which will have primary authority over implementation, will carry out the executive orders. Critics said these were steps toward mass deportation.

Kelly's memos begin to solidify the Trump administration's immigration enforcement goals, but there are still many questions left unanswered — about funding, staffing and operational tactics, among others.

While visiting Guatemala on Wednesday, Kelly reportedly reassured officials that there won't be mass deportation and that his department "will be focused precisely on those people who represent a security threat or who have committed a crime," Guatemalan President Jimmy Morales said, according to The Associated Press.

Most of the policies and programs being implemented are now under thorough review, according to sources at the department. There are some key differences between the Obama administration's immigration policies and the new plans under Trump.

Here's some of what has changed and what has stayed the same:

Enforcement priorities

Under the executive order Enhancing Public Safety in the Interior of the United States, which was signed on Jan. 25, Immigration and Customs Enforcement will "not exempt classes or categories of removal aliens from potential enforcement," according to one of the DHS memos.

They make it clear that anyone who is in violation of immigration laws may be subject to arrest, detention and deportation from the U.S.

White House press secretary Sean Spicer said Tuesday that the message from the White House is that those who "pose a threat to our public safety or have committed a crime will be the first to go" and added that the administration will aggressively make sure this happens.

When asked if mass deportation is a goal of the Trump administration, Spicer said, "No. What we have to get back to is understanding a couple of things. There is a law in place that says if you are in this country illegally, that we have an obligation to make sure the people who are in our country are here legally."

But critics disagree.

"These memos confirm that the Trump administration is willing to trample on due process, human decency, the well-being of our communities and even protections for vulnerable children in pursuit of a hyperaggressive mass deportation policy," said Omar Jadwat, the director of the ACLU's immigrants' rights project.

In 2014, Jeh Johnson, the DHS secretary under President Barack Obama, instructed all the relevant agencies to exercise prosecutorial discretion — deciding, for example, whom to stop, arrest, detain and grant parole — while enforcing the nation's immigration laws.

Johnson wrote that "due to limited resources," law enforcement officers and federal attorneys should prioritize illegal aliens who pose a threat to national security, border security and public safety.

The second priority was aliens with misdemeanor convictions and recent border crossers. All other immigration violators, even those with final orders of removal, were the last priority.

Resources were dedicated to deporting people by priority.

Under the new order, all removable immigrants are eligible for deportation. However, ICE has been instructed to continue to "prioritize several categories of removable aliens who have committed crimes, beginning with those convicted of a criminal offense."

"If these laws are not good laws, then I would highly encourage the legislators in our country to change the law. Until they are changed, people like me and ICE and other private citizens can't pick and choose the laws they are going to obey," Kelly told ABC News during a tour of the U.S.-Mexico border earlier this month.

In practice, ICE will continue to carry out targeted operations of criminals and national security threats, but if other unauthorized immigrants come into contact with ICE, they too could be deported or put into deportation proceedings, according to sources familiar with operations under the Trump administration.

Sanctuary cities

Trump has made no secret of his disdain for so-called sanctuary cities, whose policies vary but in most cases provide some protections to unauthorized immigrants by not fully cooperating with federal immigration authorities.

Trump has repeatedly called for cutting federal funding to these cities. They include major cities such as New York City, Los Angeles, Washington, Seattle and Boston.

In the summer of 2015, ICE implemented the Priority Enforcement Program (PEP) to try to establish a better working relationship with local law enforcement by agreeing to focus on individuals who pose a danger to public safety.

"With the implementation of [PEP] in July 2015, many law enforcement agencies, including some large jurisdictions, are now once again cooperating with ICE," said an ICE spokesperson in November of last year.

In 2015, during testimony to Congress, then–ICE Director Sarah Saldana said PEP was tailored to "bring back on board those state and local jurisdictions that had concerns with or legal obstacles to assisting us in implementing Secure Communities."

The first iteration of Secure Communities, a DHS program launched in 2008, was highly controversial, using fingerprints taken when someone is arrested to automatically check the person's immigration status. Critics accused the program of being unconstitutional and counterproductive.

The Trump administration has abolished PEP and restored Secure Communities, directing its personnel to take enforcement action consistent with the priorities set forth in the executive orders.

Some cities that disagreed with the policy responded by refusing to honor detainers, a tool that ICE uses to keep arrested unauthorized immigrants in custody longer.

It's unclear what the outcome of the policy shift will be, but many sanctuary cities have already affirmed their opposition to Trump's policies.

Dreamers

As of now, the Deferred Action for Childhood Arrivals (DACA) program remains intact.

Obama instituted the policy to allow unauthorized immigrants who arrived in the U.S. as children, called Dreamers, to come out of the shadows and pay a fee to receive temporary work authorization and protection from deportation.

To qualify for DACA, immigrants have to prove they were under age 31 as of June 15, 2012, came to the United States before age 16, lived here for at least five years continuously, attend or graduated from high school or college and have no criminal convictions.

Roughly 750,000 people were issued temporary protected status and, separately, work authorizations.

The only two Obama-era memos that were left untouched by Trump's executive orders were those pertaining to DACA and the parents of U.S. citizens or permanent residents.

When asked about DACA, Spicer said Tuesday it is not "what is being dealt with now."

Resources

The Trump administration has called for vastly expanding resources on immigration enforcement.

ICE is working on a hiring plan to bring on an additional 10,000 agents and officers, as well as additional operational and mission support and legal staffers. This will likely take years to implement.

Federal law enforcement agencies — and police agencies more broadly — are having a difficult time keeping staff levels at current levels, let alone upping them.

After the orders were issued, ICE increased its detention capacity by approximately 1,100 beds.

The agency is defining contracting requirements to support what it says is "the further need for increased detention capacity, particularly along the southwest border."

A list of potential detention locations is under review, according to ICE.

Funding for these increases is yet to be determined.

Jack Date and Serena Marshall contributed to this story.