The highest court's fast-track review of a federal judge's ruling striking down the law sets the stage for a momentous decision by late June on the separation of powers between Congress and the presidency.
The case will be argued before the justices on April 27.
U.S. District Judge Thomas Hogan invalidated the line-item veto law earlier this month, a blow to what President Clinton and the Republican-led Congress consider a key to fighting wasteful "pork-barrel" projects.
Congress in 1996 made Clinton the first U.S. president with such authority, and last year he used it 82 times. If the line-item veto law is upheld by the Supreme Court, Congress is likely to restore 38 of those items with two-thirds majority votes in both the House and Senate.
Hogan's ruling said the 1996 decision wrongly "crosses the line between acceptable delegations of rule-making authority and unauthorized surrender to the president of an inherently legislative function, namely the authority to permanently shape laws and package legislation."
The Constitution ... dictates that once a bill becomes law, the president's sole duty is to "take care that the laws be faithfully executed," Hogan wrote. "His power cannot expand to that of 'co-designer' of the law that is Congress' domain."
In the appeal acted on Friday, Justice Department lawyers argued that Congress did not let the president unlawfully usurp its power.
They said the law "vests the president with authority to determine ... whether items of spending that Congress has appropriated will in fact be spent. That grant of authority is fully consistent with historical practice."
The line-item veto law was a major provision of the 1994 Republican "Contract with America" campaign manifesto, and it was the only provision endorsed by Clinton. Numerous past presidents had unsuccessfully sought such authority.
The Supreme Court last June cleared the way for Clinton's use of the line-item veto by ruling that six members of Congress lacked the proper legal standing to challenge the law. But the justices said then that the law could be challenged by anyone affected once the president actually used it.
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