Presidents since at least Andrew Jackson have issued statements as they signed legislation into law, but Samuel A. Alito Jr., President Bush's Supreme Court nominee, helped to introduce an innovation in that practice when he was a lawyer in the Reagan administration.

The new twist, as Edwin Meese III, then the attorney general, explained in a Feb. 25, 1986, speech, was to urge courts to look to the president's signing statement for evidence of "what that statute really means." Earlier presidential signing statements were, by contrast, bland proclamations, instructions to subordinates about how to execute a new law or a statement of disagreement with a part of a law.

The Supreme Court has not addressed the question of whether and how the courts should make use of interpretive signing statements, and references to the issue in the lower courts are sparse.

In one 1989 decision, the federal appeals court in New York took account of a statement signed by President Ronald Reagan in connection with a sentencing law because "the executive branch participated in the negotiation of the compromise legislation."

Other courts have said or suggested that presidential statements, as one of them put it, "lack persuasive authority."

A 1987 article in The Harvard Journal on Legislation, by Marc N. Garber and Kurt A. Wimmer, examined the constitutionality of the Reagan administration's signing statements.

"The United States courts must," it concluded, "in order to quiet the boundaries of power, unequivocally reject as constitutionally unreliable any presidential signing statements offered as evidence of Congressional intent. Any lesser action will result in a realignment of authority under the Constitution, with dangerous concentration of uncheckable power in the hands of the executive."