The Metropolitan Washington Airports Authority, which operates Reagan and Dulles airports, disagrees with recently signed federal legislation that expands the size of its board and appears prepared for a legal fight.

The board of the authority retained outside legal counsel from the firm of Jenner & Block and received a 24-page review on the legality of federal legislation that increased the size of the board to 17 members from 13.

Charles Snelling, chairman of the airports authority board, wrote in a Dec. 1 letter to Virginia Congressman Frank Wolf, who introduced the bill, that the board’s outside counsel’s opinion is that “the new legislation is not operable” until Virginia and the District approve changes to the “governing MWAA compact.”

The legislation, Snelling wrote, authorizes Virginia and the District to change the compact, but not “unilaterally bringing about that amendment itself.”

Snelling said in the letter that the legal opinion “will not permit” two new members who were recently appointed by Gov. Robert F. McDonnell to “participate in board duties until the appropriate changes are made to the governing MWAA compact.”

The airports authority oversees the operations of Reagan National and Dulles International airports and is the lead oversight agency in building the 23-mile Metro line to Dulles and Loudoun County. The rail line is being built in two phases — with the first phase currently under construction and expected to open in late 2013.

The MWAA has been criticized over how it operates and for its management of the 23-mile Dulles rail project. Phase 1, which is under construction from Falls Church to Reston, could run as much as $150 million over budget. The inspector general for the U.S. Department of Transportation is conducting an audit of MWAA that will reportedly be be completed in the spring.

In November, McDonnell appointed Todd Stottlemyer of Oakton and Caren Merrick of McLean to the two new seats for Virginia on the board.

The District and Maryland would each get one additional seat on the airports authority board. Before the bill was passed, Virginia had five representatives, the District and the federal government had three, and Maryland had two.

Wolf’s legislation also prohibits members from serving past the end of their terms. Members could also be “removed for cause.” The governors of Maryland and Virginia and the mayor of the District could remove their respective members. The executive branch of the federal government already had that authority.

The airports board voted in September to authorize Chairman Charles Snelling to publicly oppose Wolf’s efforts.

On Thursday, Wolf said he disagreed with Snelling and the board’s legal counsel, saying they “have to follow the law.”

He said the legislation was meant to bring on “new people and by changing people on the board it brings people with a business approach so we can keep tolls down and finish that [Dulles rail project] on time and bring it in below budget, if possible.”

“They’re ruining the credibility of the airports authority by fighting this,” Wolf said.

“They’re ultimately going to lose. They’re just dragging this thing out.”

Follow me on Twitter @postmetrogirl.