Just a year ago, President Obama was among those who doubted he had the power to halt deportations of millions of immigrants living in the country illegally.
Asked in a 2013 Telemundo interview whether he would heed calls to expand his deportation-deferral program to include more immigrants, Obama said, "If we start broadening that, then essentially I would be ignoring the law in a way that I think would be very difficult to defend legally, so that's not an option."
Now Obama is poised to announce what it is likely to be his most ambitious and controversial plan to address the immigration issue, offering temporary reprieve from deportation to as many as 5 million additional immigrants.
Details have not been announced, but Republicans are already calling the president's plans illegal and beyond his authority.
Although the program is likely to push the limits of presidential power, immigration law experts predict opponents will have a hard time stopping him. Courts have historically given the executive branch broad leeway to decide how to enforce deportation laws for the estimated 11 million immigrants living and working in the country without legal status.
The administration is expected to present the plan as a temporary shift in the government's policy for enforcing deportation — which is widely seen as within the president's authority — as opposed to a change in immigration law or a path to citizenship.
UCLA law professor Hiroshi Motomura has been a leading voice for the view that enforcement policy is entrusted to the president.
"He cannot change the rules for granting permanent resident status or putting noncitizens on a path to citizenship," Motomura said. "But he has the legal authority to set priorities for enforcement." That may include giving "temporary reprieves to a significant number of unauthorized migrants."
It's a power that has been used by most presidents over the last 70 years. President Kennedy shielded Cubans who arrived on U.S. shores. President George H.W. Bush, building on similar executive action taken by President Reagan, shielded an estimated 1.5 million children and spouses of immigrants who'd been granted amnesty under a 1986 law. Both presidents acted alone after Congress declined to include the immigrants' family members.
"That is a strikingly close parallel to what President Obama is considering," said Stephen Legomsky, a law professor at Washington University in St. Louis and former chief counsel for immigration at the Department of Homeland Security.
The Supreme Court ruled two years ago that the executive branch had "broad discretion" in setting deportation policies. The case involved a confrontation between Arizona officials and the Obama administration over the state's plan to arrest immigrants who were living there illegally. To the surprise of state officials, the high court, including Chief Justice John G. Roberts Jr., declared that Obama had the power to block Arizona's strict enforcement plan.
Although only Congress can decide who can become a citizen, the justices said, the executive branch decides whom to deport among the millions in the nation illegally.
"The principal feature of the removal [deportation] system is the broad discretion exercised by immigration officials," including the power to decide "whether it makes sense to pursue removal at all," Justice Anthony M. Kennedy said.
Obama has refused to discuss the details of his pending executive action, but he denied last week that he had switched his views in the last year. "My position hasn't changed," he said.
But asked whether Obama stood by his comments to Telemundo, White House spokesman Josh Earnest said Tuesday that the president had subsequently solicited legal advice from the Justice Department about what he could do.
"Obviously, there are some things that have changed in this," Earnest said. "We have been in a situation where the president has ordered a broader, in-depth review of the existing law to determine what sort of executive authority does rest with the presidency to determine what kinds of steps he could take on his own."
Obama said last week that he could make a change that "falls within the realm of prosecutorial discretion."
This refers to the familiar idea that those who enforce the law cannot pursue every lawbreaker. No one expects police officers to stop and ticket every motorist they observe driving faster than the posted speed limit. Federal drug agents regularly choose to go after those who deal heroin or cocaine and not those who possess marijuana, even though both are illegal under the same anti-narcotics law.
Those urging Obama to act say the government has no choice but to engage in selective enforcement, noting that Congress has only provided enough money to deport about 400,000 immigrants per year. The Obama administration says it focuses deportation on gang members, terrorism suspects and criminals such as smugglers.
But critics argue that a president's enforcement discretion should be limited to individuals and case-by-case decisions — not used as an end-run around Congress to implement broad changes that exempt large groups.
"Only Congress can decide which large categories of immigrants can be admitted," said Jessica Vaughan, director of policy studies for the conservative Center for Immigration Studies in Washington. If the president suspends enforcement against "a huge class" of immigrants, she said, that is "not truly prosecutorial discretion, but an abuse of executive authority."
Congressional Republicans liken the president's actions to amnesty. By also offering immigrants work permits, critics say, Obama is trying to implement an immigration overhaul without Congress.
"The president does not have the authority to amend, suspend and rewrite our immigration laws," said House Judiciary Committee Chairman Robert W. Goodlatte (R-Va.).
Though the Senate passed a bipartisan immigration bill in 2013, the House has refused to act, mainly because Republicans remain deeply divided on the issue.
But even some immigration experts who served in Democratic administrations are wary of a broad shift in enforcement policy.
"There is a lot of gray area" in the immigration laws, said University of Virginia law professor David Martin, who worked in the Clinton and Obama administrations. While the executive branch has a "fairly wide scope" for enforcing the law, a policy that shields large groups of immigrants "starts to sound like lawmaking. It would skate to the very edge of the president's discretion if he were to exempt a very large group from enforcement," Martin said.
In 2012, Obama launched a deportation-deferral program called Deferred Action for Childhood Arrivals, which has granted relief to 680,000 immigrants, the so-called Dreamers, who were brought to the U.S. illegally as children.
Legal challenges to the program failed. Two years ago, U.S. immigration agent Chris Crane and the governor of Mississippi sued in federal court in Dallas to challenge Obama's deferred action order, pointing to a law that says all arriving immigrants should be held for deportation. They contended the president's deportation-deferral order for the children was illegal.
Even though the judge said the claim was "likely to succeed" on its merits, he dismissed the lawsuit on the grounds that neither the state nor the immigration officers had legal standing to contest the issue. Experts say opponents of Obama's next move on immigration will encounter similar difficulties in pressing a legal case.