What's a constitutional crisis -- and are we in one?

(CNN)Less than two weeks into Donald Trump's presidency, the United States is staring down the barrel of a crisis echoing the fraught final months that ended with Richard Nixon's resignation in August 1974.

"I have not seen either lawless behavior or civil servants calling out lawless behavior like this since (the Watergate era)," Seth Kreimer, the Kenneth W. Gemmill Professor of Law at the University of Pennsylvania, told CNN on Monday night as Donald Trump was replacing an acting attorney general who would not defend his executive order with one who would.
But does it rise to the level of a constitutional crisis?
"No -- not yet," said Jennifer Chacón, professor at the University of California Irvine School of Law. "A crisis would be a situation where there was a genuine concern that one branch of the government was not acting constitutionally and no checks seem to be operating on that branch."
Every American school kid learns about the three branches of the US government, elegantly woven together by the Founders to provide checks and balances on each other. News of an attorney general refusing to follow a presidential order, or DHS employees not complying with a court ruling, is unusual and unnerving things in a country where baseline political norms and institutional control in government have prevailed almost uninterrupted for decades.

The slippery slope

But concerns were highlighted over the weekend, as disputes broke out at airports around the country and in the courts over Trump's executive order blocking or suspending the entry of immigrants and refugees into the US turned chaotic. Protesters and lawyers clashed with airport border patrol agents before a federal judge temporarily halted the deportation of people detained under the murky auspices of White House ban.
"We saw mass confusion at the level of (airport) line agents because we had an executive who crafted an executive order without consultation with any of the usual suspects you'd normally consult with," Chacón said, referencing reports that the Department of Homeland Security, State Department and congressional officials were left in the dark about the order right up to its dizzying implementation.
The messy scenes that followed, including an incident relayed in court documents when lawyers were denied access to arriving refugees by a customs clerk who referred their questions to Trump himself, laid the traps for a more fundamental crisis.
"What we're seeing (in the airports) and what I'm concerned about is an administration that acts rashly and fails to consult in ways that generate the possibility and create the likelihood that executive agents will operate in violation of court orders," Chacón said.

The Monday night massacre

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The fight carried over into Monday, when the acting attorney general, Sally Yates, instructed Justice Department lawyers not to defend the order in court, while openly questioning whether the administration was acting in accordance with its own order. She was promptly sacked and replaced by the White House, which said in a statement Yates had "betrayed" the Justice Department.
Trump was acting within his rights in his decision to fire Yates and replace her with Dana Boente, the US attorney for the Eastern District of Virginia, who was sworn in late Monday night.
But the episode reminded a certain generation of the Richard Nixon's infamous "Saturday Night Massacre," when in October 1973 he ordered his attorney general to fire the special prosecutor, Archibald Cox, in charge of investigating the Watergate scandal.
Attorney General Elliot Richardson resigned rather than follow Nixon's orders. His deputy, Deputy Attorney General William Ruckelshaus also stepped down in protest. By the next morning, Nixon had eliminated the office of the special prosecutor and returned the now rapidly erupting scandal to what remained of the Justice Department.

On the edge of crisis

Yates in her statement explaining the decision not to defend Trump's executive order, stopped short of resigning her position, but suggested the White House had purposefully overreached its authority, as defined the text of the ban, in its public comments.
The review by the Office of Legal Counsel, which signed off on the document, "does not take account of statements made by an administration or it surrogates close in time to the issuance of an Executive Order that may bear on the order's purpose," she said. "At present, I am not convinced that the defense of the Executive Order is consistent with these responsibilities nor am I convinced that the Executive Order is lawful."
The arrival of a new, Trump-appointed attorney general, likely in the form of Alabama Sen. Jeff Sessions, should defuse the current showdown. But the questions elevated over the weekend are expected to linger as more of the administration's flurry of early executive orders are challenged in the courts.
As of Monday, at least five states -- Virginia, New York, Massachusetts, Washington and California -- planned to argue against it in federal court. How the White House and civil servants working for executive agencies respond to those coming decisions will write the next chapter.