Sen. Jeff SessionsJeff SessionsStates hope Trump era will reset federal relationship Protests, anti-Trump events offer inauguration alternative Senate seeks deal on Trump nominees MORE (R-Ala.) blasted Homeland Security Secretary Janet Napolitano upon news of her resignation Friday, saying her tenure was "defined by a consistent disrespect for the rule of law."

Napolitano said Friday that she was resigning her Cabinet post to become the next president of the University of California system.

"The resignation of Secretary Napolitano should refocus the attention of Congress on its first task: to ensure that the executive branch faithfully carries out the laws of the land," Sessions, a member of the Senate Judiciary Committee, said in a statement. 

"The most significant obstacle to immigration reform remains President Obama’s selective enforcement of the law. Any selection — interim or permanent — to replace Secretary Napolitano must disavow these aggressive non-enforcement directives or there is very little hope for successful immigration reform. 

"Whoever replaces Secretary Napolitano must restore the rule of law, as well as the morale of ICE officers which has plummeted under her tenure.”

The former Arizona governor has been the target of frequent conservative criticism during her time in the Obama administration, with frustration over the president's decision to defer the deportation of illegal immigrants who entered the country as children earning particular ire. 

Sessions aides on Friday pointed to a lawsuit filed by agents with Immigration and Customs Enforcement who argued the president's mandate “commands ICE officers to violate federal law” and threatens them with suspension or termination if they do not comply.

"Agents are forced to apply the DREAM Act, not to children in schools, but to adult inmates in jails, releasing criminals back into communities throughout the nation, criminals who have committed felonies, assaulted our officers, and who prey on children," said Chris Crane, a deportation officer who leads the union of immigration enforcement agents, at an April press conference with the Alabama lawmaker.

Other Republicans were more muted in statements marking Napolitano's resignation. House Homeland Security Committee Chairman Michael McCaul (R-Texas) said that while "Secretary Napolitano and I have disagreed on issues like the security of the border, I respect and thank her for her service."

Sen. John McCainJohn McCainUS democracy is in crisis. Trump voters must help us get past it. The rise of Carlson, and the fall of Van Susteren Booker to vote against Tillerson MORE (R-Ariz.) noted "we have had our share of disagreements during her time as Secretary, but I have never doubted her integrity, work ethic or commitment to our nation’s security."

"The people of Arizona can be very proud of our former Governor’s service, and I wish her all the best as she assumes leadership of the nation’s largest public university system," he continued.