Under investigation by the U.S. Department of Transportation's inspector general and the FBI, the embattled Metropolitan Washington Airports Authority is also facing a legal challenge to its plan to extend Metrorail to Washington Dulles International Airport and beyond.

On Oct. 2, the U.S. Court of Appeals for the Federal Circuit heard oral arguments in a class-action lawsuit claiming that the MWAA has no legal authority to raise tolls on the Dulles Toll Road in order to pay for the Silver Line.

The case was dismissed by a lower court in July. In their appeal, lawyers for American University law professor John Corr and John Grigsby, a Northern Virginia resident who uses the toll road for his daily commute, made three key points:

1. MWAA's tolls are set above the level needed to operate and maintain the toll road, which would constitute a user's fee. They therefore constitute a tax.

2. Such a tax is an unconstitutional "illegal extraction" because MWAA's compact does not give it any taxing power.

3. The MWAA, which was created by the federal government solely to operate two federally owned airports -- Dulles and Ronald Reagan Washington National -- is independent of any governmental body, either at the local, state or federal level. Lacking any accountability to elected officials, MWAA's tax hikes violate the due process clause of the U.S. Constitution.

The appellants quoted a 1995 Supreme Court ruling in a case involving Amtrak: "It surely cannot be that government, state or federal, is able to evade the most solemn obligations imposed by the Constitution by simply resorting to the corporate form."

The board's recent behavior -- the subject of two federal investigations -- provides a good example of what happens when power is delegated to political appointees without the proper checks and balances. When Congress approved the original multistate compact that created the MWAA to operate the two federal airports, it did not give the MWAA authority to impose taxes on Virginia citizens. The Virginia Constitution also forbids the state legislature from delegating its own constitutional taxing authority.

By ignoring these constitutional protections and assuming a power that it has never been granted, the MWAA has become a rogue entity. Its board thinks itself beyond the reach of the same federal government that created it in the first place. This sets an extremely dangerous precedent. So even if the Appeals Court unwisely rules in MWAA's favor, Congress must step in and prevent the authority's blatant usurpation of federal power to continue unchecked.