President Donald Trump has caught a lot of heat for rescinding the Deferred Action for Childhood Arrivals program with a six-month wind-down. Few people seem aware that he's ending an administrative amnesty for illegal aliens that President Barack Obama lacked the constitutional and legal authority to implement.

How do we know? Because even Obama admitted it – repeatedly.

Responding in October 2010 to demands that he implement immigration reforms unilaterally, Obama declared, "I am not king. I can't do these things just by myself." In March 2011, he said that with "respect to the notion that I can just suspend deportations through executive order, that's just not the case." In May 2011, he acknowledged that he couldn't "just bypass Congress and change the (immigration) law myself. ... That's not how a democracy works."

Yet in 2012, he did it anyway. He put DACA in place to provide pseudo-legal status to illegal aliens brought to the U.S. as minors, including as teenagers. He promised them that they wouldn't be deported and provided them with work authorizations and access to Social Security and other government benefits.

And he did this despite the fact that the immigration laws passed by Congress do not give the president the ability to do this. Indeed, Congress specifically rejected bills to provide such benefits.

As Attorney General Jeff Sessions pointed out this week, DACA "contributed to a surge of unaccompanied minors on the southern border that yielded terrible humanitarian consequences." Since most DACA beneficiaries are now adults, "it also denied jobs to hundreds of thousands of Americans by allowing those same jobs to go to illegal aliens," Sessions said.

The unconstitutionality of Obama's actions were confirmed when Obama tried to implement a second, similar program in 2014 called the Deferred Action for Parents of Americans and Lawful Permanent Residents program, or DAPA. Like DACA, DAPA provided an administrative amnesty for illegal aliens who came to the U.S. as adults and gave them work authorizations and access to government benefits.

The Fifth Circuit Court of Appeals upheld a nationwide injunction against DAPA, which the Supreme Court allowed to stand. As the Fifth Circuit said, the fact that the president declined to enforce the law and remove illegal aliens "does not transform presence deemed unlawful by Congress into lawful presence and confer eligibility for otherwise unavailable benefits based on that change."

Under our Constitution, Congress has plenary authority over immigration. The president only has the authority delegated to him by Congress – and Congress has never given the president the power to provide a pseudo-amnesty and government benefits to illegal aliens.

The DACA program suffers from exactly the same constitutional infirmities as DAPA. A number of states have threatened to sue the administration to stop the DACA program. In the face of that threat, Trump really had no choice. General Sessions' legal conclusion was that DACA "is vulnerable to the same legal and constitutional challenges that the courts recognized with respect to the DAPA program."

The place to have the debate about what to do about illegal aliens who were minors when they came to this country is in the halls of Congress, not the White House. Failure to correct this unilateral, unconstitutional overreach would set a dangerous precedent that weakens our constitutional balance of powers. As law professor Jonathan Turley said, "If a president can claim sweeping discretion to suspend key federal laws, the entire legislative process becomes little more than a pretense."

When it comes to immigration, Attorney General Sessions was correct when he said that the "compassionate thing is to end the lawlessness, enforce our laws, and, if Congress chooses to make changes to those laws, to do so through the process set forth by our Founders in a way that advances the interests of the nation." That is essential to preserving our constitutional republic.