And just like that, U.S. President Donald Trump has casually thrown the futures of 800,000 people into a cruel limbo.

On Tuesday, the White House, fulfilling one of Mr. Trump's campaign promises, ended the Deferred Action for Childhood Arrivals (DACA) program, an initiative launched by former president Barack Obama in 2012 to protect the children of illegal immigrants from deportation.

The White House says it will not start removing these people's protected status for six months, in the hopes that Congress can use the time to pass a law allowing the 800,000 to stay.

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Konrad Yakabuski: Why America must remain a country of 'DREAMers'

But given that the Republican-controlled Congress is so dysfunctional that it couldn't pass a kidney stone if its life depended on it, Mr. Trump has put a gun to the heads of some of the most vulnerable people in his country, all for the sake of appeasing his shrinking base.

Thousands of people from Mexico, Central America and South America who were brought to the U.S. by their parents when they were kids, and who have never had a legal path to citizenship, could face deportation as early as next March.

Aged today between 15 and 36, these people have lived precarious existences their entire lives, through no fault of their own, in the only country they have ever really known.

The DACA program, to which they had to apply individually once they turned 15, gave them the opportunity to legally study and work in the U.S. for two years, with the possibility of repeated renewals.

They didn't get citizenship but they were not subject to deportation, so long as they met conditions such as having a high-school degree and no criminal record, and if they came to the U.S. as children before 2007.

Mr. Trump's upending of that small mercy is of a piece with his anti-immigrant rhetoric and nativism. His claim that he did it to protect the rule of law and the authority of the courts is laughable in the wake of his pardon of the criminally convicted Arizona sheriff, Joe Arpaio.

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As well, he has passed the buck with his usual feckless guile. "Congress, get ready to do your job – DACA!" he tweeted on Tuesday morning. His decision, somebody else's problem.

The question of what to do with the children of illegal immigrants has dogged Washington for two decades. Congress tried to solve the problem in 2001 with the DREAM Act, a bill that would have given some of the children a path to citizenship. It was passed by the House, but couldn't get enough votes in the Senate.

Further efforts to solve the problem went nowhere, prompting Mr. Obama to use his executive powers in 2012 to defer deportations of so-called DREAMers for two years at a time, and to allow them to work in the meantime.

But it was never meant to be a permanent solution, since only Congress has the power to legislate that.

By killing Mr. Obama's executive order at a time when there is public sympathy for the plight of the DREAMers, and when business groups are calling on the White House to keep them in the country, there is a small chance that Mr. Trump's decision will actually help them.

Congress faces two options: Pass legislation along the lines of the DREAM Act within six months; or fail to do so, and go into mid-term elections next year just as the pace of deportations of DREAMers picks up.

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There are Republicans in Congress who support DREAM-like legislation. Mr. Trump has even expressed sympathy for DREAMers, to the extent that he is capable of that normal human emotion.

But there's a catch. Mr. Trump ran, and won, as the candidate shouting loudest against illegal immigration. Many Republicans in Congress agree with that stance; those who don't, risk facing a nomination challenge before the 2018 mid-term elections from hard-liners energized by Mr. Trump's nativism. To protect themselves, even pro-DREAM Republicans might have to vote against a bill that would be seen as favourable to illegal immigrants, no matter how humane the law might be.

So while Mr. Trump didn't create the original problem, and he is correct to say that only Congress can solve it once and for all, he is entirely responsible for manufacturing the current crisis. His hateful rhetoric could well come back to haunt 800,000 people who have grown up in the U.S., have respected the law and made themselves into valuable members of society, but who could never be "American" enough in the eyes of the President's supporters.

They will have to return to countries they never knew, or choose to disappear into America's sea of undocumented immigrants. It's possible some of them will decide to make their way to Canada.

Whatever the outcome, Mr. Trump's vow to make America great rings more hollow than ever.