Now that President Trump has handed Congress the fate of nearly 1 million illegal immigrants who arrived in the United States as minors, a key question is whether lawmakers can resolve the issues that killed the bill that would have spared them this legal limbo.

Every failure of major immigration legislation for the past dozen years can be explained by a past failure. "Comprehensive immigration reform" is a nonstarter for many conservatives because the 1986 Immigration Reform and Control Act did not deliver on its enforcement promises and did not reduce illegal immigration. (There's a reason people still boast of the tax reform passed 31 years ago but seldom tout that year's immigration reform.)

Similarly, the Deferred Action for Childhood Arrivals program is literally the product of Congress' inability to pass he DREAM Act.

Former President Barack Obama initially sought to build support for immigration reforms that would legalize most of the illegal immigrants already in the country by trying to demonstrate his commitment to enforcement by citing a high number of deportations.

While immigration hawks remained dissatisfied because the removal numbers were misleading (a Google search for "Obama cooked the books deportations" produces over 2.7 million results), liberal activists disliked their president being perceived as the "deporter-in-chief."

Obama repeatedly downplayed his legal authority to remedy the undocumented population's problems through unilateral executive action over progressive objections. "If, in fact, I could solve all these problems without passing laws in Congress, then I would do so," he said in 2013. "But we're also a nation of laws … The easy way out is to try to yell and pretend like I can do something by violating our law."

"The problem," Obama said earlier that year, "is that I'm the president of the United States, I'm not the emperor of the United States."

Yet Obama grew frustrated by Congress' unwillingness to pass the immigration bills he wanted, especially one targeting a sympathetic subgroup of illegal immigrants who wanted to go to college or join the military, were mostly here through no fault of their own and had known no other country besides the United States — the DREAM Act.

The Obama Department of Homeland Security began clandestinely studying ways the administration could achieve the same policy outcomes as these laws through executive actions. These discussions became known through leaked memos. DACA and an initiative aimed at the Dreamers' parents that never took effect were the eventual results.

Going beyond mere prosecutorial discretion by issuing work permits to people Congress had specifically declined to legalize, these executive actions raised widespread legal and constitutional questions. But there was also a broad consensus, with a few dissenters, that most of the people eventually covered by DACA probably shouldn't be deported.

So why then couldn't Congress come to an agreement to fix this problem the right way, through the legislative process? The failure of the DREAM Act is usually blamed on bad, possibly racist, motives and general Republican intransigence.

The latter is where Obama pinned the blame after Trump announced he was rescinding DACA with a six-month delay for Congress to act. "[F] or years while I was President, I asked Congress to send me such a bill," he said in a Facebook statement. "That bill never came."

Except that is not entirely true. There were three major objections to the DREAM Act as it was written that went beyond a categorical opposition to legalizing any unauthorized immigrants, a position taken by some but not most Republicans. It created incentives for future illegal immigration by adults bringing young children with them; it did not adequately guard against applicants' fraud; some felt that the age cutoff at 16 was too high.

This came after years of worry that previous bills would repeat the 1986 enforcement bait-and-switch.

Sen. Tom Cotton, R-Ark., suggested he could support legalization if it were coupled with measures to address the first objection: the direct incentive for future illegal immigration that is inherent in an amnesty no matter what strings are attached and the indirect one that comes from beneficiaries who can then sponsor extended family members as immigrants.

"Thus, we must mitigate these consequences by stopping the chain migration that hurts the working class and by strengthening the enforcement of our immigration laws," Cotton said after Attorney General Jeff Sessions' DACA announcement.

It might be a bit much to attach the full RAISE Act, a Cotton-sponsored bill that would among other things cut legal immigration in half over 10 years, though it is an understandable opening bid from conservatives whose immigration-policy views were shut out of the debate under both Obama and former President George W. Bush.

But could some concessions be made to those want a legislative fix without the increases in illegal immigration seen after past amnesties since 1986? It's the stuff that DREAMs are made of.