(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.

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