First of all, the claim that DACA was unconstitutional is false. While the Obama administration preferred a legislative immigration solution, it is unequivocally the legal responsibility of the executive branch to set enforcement priorities.
It is also highly misleading to say that DACA contravened the policy established by Congress. The legislature has appropriated enough funds to deport only a small fraction of authorized immigrants; the executive branch using its discretion to determine which deportations were the highest priority is a known and inevitable consequence of the policy choices made by Congress. It was plainly constitutional for the Obama administration to determine that scarce resources would not be expended deporting law-abiding people who often have known no other home besides the U.S. — and it was also humane for those priorities to be made explicit.
In addition to his erroneous legal arguments, Sessions misrepresented DACA’s consequences. His assertion that DACA had “contributed to a surge of unaccompanied minors” trying to immigrate illegally is false. There is no evidence that any such surge is happening at all, not to mention the fact that people who came to the U.S. after DACA was implemented are ineligible for its protections.
Still, one of DACA’s great weaknesses is that it was much easier to reverse than a statute passed by Congress would have been. The best-case scenario would be if the Trump administration’s decision to phase out DACA provides an incentive for Congress to finally pass legislation that would protect the DREAMers from deportation. Republican members of Congress who were reluctant to provide Obama with any legislative wins might be more amenable to compromise with Trump in the White House. It’s possible that this won’t work out so badly.
But don’t bet on it. The internal divisions that have prevented congressional Republicans from agreeing on an anti-immigration bill haven’t suddenly disappeared. Trump winning the Republican nomination didn’t come entirely out of the blue, either; it’s worth remembering that Mitt Romney rode to the Republican nomination in 2012 in part by running aggressively to the right on immigration. There will be substantial opposition to a legislative version of DACA within the Republican conference, and the Republican leadership will be reluctant to rely on Democratic votes to pass a bill on a hot-button issue. Republicans have found the transition from obstruction to governing difficult, and this is unlikely to be an exception.
Plus, there’s an additional problem: With this Congress, the cure could well be worse than the disease. The anti-immigration faction with the Republican Party won’t allow legislation to be passed without extracting a lot of concessions. A bill that authorized some version of DACA but, say, substantially increased funding for Immigration and Customs Enforcement could be worse than doing nothing. And whatever Congress does, Trump will still be president and Sessions will still be the attorney general. A law that provides more resources to this executive branch would still be bad news for many unauthorized immigrants.