Washington (CNN) -- The Justice Department Thursday made public its legal opinion that President Barack Obama's controversial recess appointments last week are constitutional.
In an internal opinion, the Justice Department said the president has the authority to make recess appointments during pro-forma Senate sessions in which no business is to be conducted. It said the brief pro-forma sessions called for the purpose of preventing recess appointments "do not have the legal effect of interrupting an intrasession recess long enough to qualify as a 'Recess of the Senate under the Recess Appointments Clause.'"
"The president therefore has discretion to conclude that the Senate is unavailable to perform its advise-and-consent function and to exercise his power to make recess appointments," said Virginia Seitz, the assistant attorney general who heads the Office of Legal Counsel.
The opinion, dated January 6 -- two days after the president announced the appointments -- is certain to re-ignite a bitter partisan debate in which furious Republicans may attempt to block an array of other appointments and Democratic initiatives.
The opinion came from the Office of Legal Counsel, whose top lawyers are part of the Obama administration and answer to Attorney General Eric Holder, who is also appointed by the president. It controls only the actions of the administration and its agencies.
The appointments at issue are the selection of Richard Cordray to serve as the director of the new Consumer Financial Protection Bureau and three members of the National Labor Relations Board.
Republicans and their allies at the National Chamber of Commerce are not yet vowing to take the issue of legality of the appointments to a federal judge, but neither has that potential move been ruled out.
The ranking Republican on the Senate Judiciary Committee, Charles Grassley of Iowa, wasted no time in denouncing the Justice Department opinion.
"The Justice Department opinion is unconvincing. Its conclusion is at odds with the text of the Constitution and the administration's own previous statements," Grassley said in a statement released Thursday. "It fundamentally alters the careful separation of powers between the executive and legislative branches, Grassley said. "This is clearly an escalation in a pattern of contempt for the elected representatives of the American people."
Grassley dropped a warning of potential unspecified retaliation. "The Senate will need to take action to check and balance President Obama's blatant attempt to circumvent the Senate and the Constitution," he said.
Although administrations have previously considered brief "pro-forma" sessions adequate to prevent recess appointments, the Obama Justice Department declared such brief sessions are not sufficient to block appointments.
It is unusual for the Office of Legal Counsel to make its opinions public. The release of the Bush administration's so-called "torture" memos was made by the Obama Justice Department only after heated internal debate. In this case, the OLC opinion was promptly released because it provides apparent legal cover for the president's decision, and opposition appears to be entirely "across the aisle."
The move is likely to serve as a rallying cry for GOP lawmakers, who have high hopes of taking control of the Senate following the November elections.