Did President Obama change the law or not when he unilaterally decided that millions of illegal immigrants in the U.S. would be protected against deportation?

Until this week, both the president and White House staff insisted that Obama did not change the law and indeed could not change the law without the cooperation of Congress. Obama's move was just a revision of executive branch enforcement priorities, according to the official White House line. A Justice Department memo backed up the president's contention.

"This notion that somehow I can just change the laws unilaterally is just not true," Obama said at a Hispanic Roundtable meeting in the White House in 2011. "We are doing everything we can administratively." Obama said similar things several times since then, and on Nov. 18, just two days before Obama announced his action, White House spokesman Josh Earnest pointed to the "large number of cases in which the president has said, 'I'm not an emperor, I'm not a king, and I can't change the law.' "

Fast forward to Tuesday, when Obama was speaking on immigration reform to a group in Chicago. When protesters began yelling at Obama to stop all deportations, the president became frustrated and answered: "There have been significant numbers of deportations. That's true. But what you're not paying attention to is the fact that I just took action to change the law."

In an instant, Obama's insistence that "this notion that somehow I can just change the laws unilaterally is just not true" became "I just took action to change the law."

In Chicago, Obama went on to explain, "The way the change in the law works is that we're reprioritizing how we enforce our immigration laws generally." Perhaps defenders will take that to mean Obama really wasn't saying he changed the law and just meant that he had changed enforcement. But a more reasonable reading would be that Obama was suggesting his "reprioritization" of immigration law enforcement is so broad and far-reaching that it amounts to changing the law itself. That's why the president's short-version description of his move was, "I just took action to change the law."

Obama's latest statement will give new energy to Capitol Hill Republicans who argue that he did indeed change the law, and that such sweeping changes lie within the exclusive authority of Congress. Until Tuesday, Obama had been quite disciplined in how he described his authority in the area of immigration. Now, that has changed.