WASHINGTON (CNN) -- Whether involving treaties or treason, allegations of political coverup or extramarital sex, energy panels or U.S. attorneys, executive privilege is a legal and political tool whose use dates back more than 200 years.

It is often invoked by the president but rarely accepted by Congress. When power brokers from those two branches clash, it is often left to political expediency or the courts to sort out the competing interests.

The presidential power tool was asserted Wednesday when President Barack Obama -- at the request of the attorney general -- refused to turn over internal documents sought by a congressional panel over the failed "Fast and Furious" gun-running sting operation.

Executive privilege is a claim made by the president or other executive branch officials when refusing to give Congress, courts, or private parties certain information, including records and testimony.

"Congress has the power of the subpoena, and if they issue them seeking to put officials under oath, then the president can claim executive privilege," said Edward Lazarus, author of a book on the Supreme Court, "Closed Chambers." "Then you have a showdown among two co-equal branches of government, and the judiciary often becomes the referee."

The claim arises from the constitutional idea of separation of powers. The concept is not a settled legal precept, since it has been open to varying interpretation, and it remains a controversial, litigated part of government business.

"The main factor that courts usually use is internal deliberations," said CNN Senior Legal Analyst Jeffrey Toobin. "The courts want to respect the president's internal deliberations so he can get freely given advice from his aides. They don't want to invade that privilege. However, that's not an absolute privilege for everything that goes on in the White House."

Constitutional groundwork

The U.S. Constitution does not expressly mention this idea of executive privilege.

President George Washington set the precedent in 1796 when he refused a House request for documents relating to how the Jay Treaty with Great Britain was negotiated.

The Supreme Court first decided the issue in 1807, during Aaron Burr's separate trial for treason. Chief Justice John Marshall ordered President Thomas Jefferson to produce a letter that might have exonerated the former vice president. The court concluded the Sixth Amendment right of compulsory process did not exempt the executive branch.

The letter was turned over but its contents never were publicly revealed, at Jefferson's insistence. As may ultimately prove to be the case in the Fast and Furious controversy, the Burr issue was privately negotiated, without a subpoena being issued.

The high court has not spoken with one voice on the issue. In 1927 it ruled the executive branch was not protected from "legitimate" outside investigations. In 1948, presidential prerogatives were preserved in relation to private lawsuits where national security or military matters are involved.

Executive privilege claims have risen sharply since the 1950s, but most presidents since Dwight D. Eisenhower have assured Congress that such claims would only be asserted with their personal approval, as Attorney General Eric Holder indicated Obama did in this case.

Recent precedent

The biggest recent executive privilege case was U.S. v. Nixon in 1974, during the Watergate crisis. That involved a criminal grand jury subpoena for the president to turn over secretly recorded Oval Office audiotapes. The justices unanimously ruled against his legal claims, saying there was great national interest that the tapes be produced.

Nevertheless, for the first time the Supreme Court recognized the constitutional basis for executive privilege. "Nowhere in the Constitution ... is there any explicit reference to a privilege of confidentiality," that ruling said, "yet to the extent this interest relates to the effective discharge of a president's powers, it is constitutionally based."

The court then recognized that "those who expect public dissemination of their remarks may well temper candor with a concern for appearances and for their interest, to the detriment of the decision-making process."

In other words, the Supreme Court laid out a balancing test of sorts: a basic need for executive confidentiality and candor, weighed against the public interests of congressional oversight, a criminal probe or prosecution.

President Bill Clinton's first term produced an interesting legal dilemma that later popped in subsequent administrations. Then-first lady Hillary Clinton chaired a health care task force that was sued for closing to the public several meetings with government and private officials. The issue was whether she as the first lady was a government employee and therefore could claim executive privilege. A federal appeals court concluded she could.

The issue emerged again in 2001, when Vice President Dick Cheney was sued for his role chairing an energy task force. Only this time the issue was whether executive privilege applied to conversations by White House officials with those outside the government.

Cheney was taken to court by private groups and the Government Accounting Office seeking information on what energy company officials and lobbyists may have advised the group, whose conclusions later formed the basis of the administration's energy policy. A lawsuit claimed those contacts improperly benefited private energy businesses.

The private lawsuit reached the Supreme Court after two years of legal wrangling and the White House won a temporary victory. Justice Anthony Kennedy wrote, "Special considerations applicable to the president and the vice president suggest that the courts should be sensitive to requests by the government" in such appeals.

The government claimed in its legal brief it is "clear that the president's authority to receive opinions from executive officers is not subject to interference from or control by other branches" of government.

The case was sent back to the lower courts and, after about five years, was settled without the government turning over the requested documents.

The last major confrontation came in 2007, when President George W. Bush asserted executive privilege as a reason for White House Counsel Harriet Miers and White House Chief of Staff Joshua Bolten not to provide information about the controversial firing of nine U.S. attorneys.

Democrats in Congress believed the firings were politically motivated, and wanted to force the pair to testify about it.

But when Congress sued them, the case never made it to court. It was settled between the two sides, with mixed results.

The future

Time may be on the side of the White House, if it is determined to see this issue played out in the courts. The case could take many months, or even years, to be resolved.

Congress benefits from having the Fast and Furious controversy viewed as an issue of tremendous national importance, and the power of the legislature to serve as a check on the power of the executive. It has not been shy invoking the threat of subpoenas. Administration supporters have countered the request for documents by the Republican-led House Oversight and Government Reform Committee amount only to election-year politics, with the goal of embarrassing Obama.

The president has two centuries of precedent to rely on, and no clear sign the courts want to resolve the issue with some bedrock finality.

"The executive branch is taking the long-term view of this," said legal analyst Lazarus. "You need to develop golden rules in this situation that will apply regardless of who is in power, to come up with a fair way to hold the president accountable without unduly chilling speech with the executive branch."