The letter is at least partially in response to critics, many who call Obama's unilateral decision to extend deportation relief and work permits to 4.7 million illegal immigrants unconstitutional and illegal.
"While we differ among ourselves on many issues relating to Presidential power and immigration policy, we are all of the view that these actions are lawful," the professors wrote. "They are exercises of prosecutorial discretion that are consistent with governing law and with the policies that Congress has expressed in the statutes that it has enacted."
The "setting of removal priorities and the use of deferred action" has been "used many times by the executive branch under presidents of both parties, and Congress has explicitly and implicitly endorsed their use," they wrote.
Signatories include three law professors from the University of Chicago - where Obama previously taught constitutional law - along with Columbia University President Lee Bollinger, Harvard Law School Professor Laurence Tribe, Adam Cox from New York University School of Law and former Yale Law School Dean and former State Department Legal Advisor Harold Hongju Koh.
The Department of Justice also released on Thursday the memo it prepared for Obama as legal advice detailing why it believes the president's actions are lawful.
"We conclude that DHS's proposed prioritization policy and its proposed deferred action program for parents of U.S. citizens and lawful permanent residents would be permissible exercises of DHS's discretion to enforce the immigration laws," the department wrote.
The memo does warn Obama not to stray into gray areas of the law not already set by precedent.
"The Executive cannot, under the guides of exercising enforcement discretion, attempt to effectively rewrite the laws to match its policy preferences," wrote Principal Deputy Assistant Attorney General Office of Legal Counsel Karl Thompson.
"An agency's enforcement decisions should be consonant with, rather than contrary to, the congressional policy underlying the statutes the agency is charged with administering."
Interestingly included in the memo is the department's conclusion that Obama doesn't have the legal authority to provide broad deportation relief to parents of those who were provided amnesty through the 2012 Deferred Action for Childhood Arrivals (DACA) program.
"As it has been described to us, the proposed deferred action program for parents of DACA recipients would not be a permissible exercise of enforcement discretion," said the department.
Also revealed in the memo is a footnote describing how Justice Department lawyers raised legal concerns over the 2012 DACA program.