But she cautions that unanswered legal questions about the DACA program and how Trump chose to go about ending it create a sizeable grey area on extending the deadline.
"It depends on whether or not you think the original program was unconstitutional. And that has not been decided by the courts," said Brown, now with the Bipartisan Policy Center. "The September order gave a six-month wind-down to give people a period of time to adjust. Now, whether or not he had the authority to extend it that long has never been tested in court.
"So we don't really know if an extension would be accepted by the legal system," she said. Further muddying the waters: It is unclear whether a second order would be challenged in court; but issuing a new one could force Justice Department attorneys to alter their arguments about the legality of the September missive, creating "some bit of legal jeopardy in issuing another order."
Just what Trump and his top aides will decide to do if Congress is unable to come up with an immigration deal that addresses DACA is anyone's guess.
When the president popped in on a meeting Kelly was having with reporters about a White House immigration plan on the evening of Jan. 24, he signaled he was considering extending the deadline if immigration talks need more time. But he was clear about his stance on whether he has the authority to do so.
"I certainly have the right to that, if I want," he said.
But that came eight days after Nielsen told the Senate Judiciary Committee just the opposite. Senate Democratic Whip Richard J. Durbin of Illinois asked her if she has concluded Trump lacks the legal power to change the deadline. "Yes," she replied.
Nielsen's department, however, struggled to clarify the disconnect between the two camps' opposite stances.
Acting DHS press secretary Tyler Houlton sent Roll Call a lengthy statement when asked to spell out the legal underpinning of Nielsen's stance. "Given the attorney general's determination that the previous DACA policy was likely unlawful and unconstitutional, the administration is fully committed to that deadline," Houlton said.
The statement did not directly address the legal basis, other than to stress the president determined DACA unconstitutional. He also claimed Nielsen had never said Trump lacks the authority to set a new deadline, and then did not respond to a follow-up email when a reporter shared the Durbin exchange from a transcript of the Jan. 16 hearing.