Senate Republicans told the 9th Circuit Court on Friday to cancel its mid-August trip to Hawaii, saying the court failed to prove why the trip was necessary even though it had been given weeks to respond.

The GOP lawmakers are also threatening legislation to bar such junkets in the future.

"In our initial letter, we requested specific documents pertaining to the total cost of the conference but were given vague excuses instead," Sens. Jeff Sessions, of Alabama, and Charles Grassley, of Iowa, wrote to the Ninth Circuit Judge Alex Kozinski. "The Court sidestepped every request for documentation of expenditures, responding instead that travel-related expenses are not easily accessible."

The senators in May asked the court to justify the trip, which could cost taxpayers as much as $1 million, following a congressional investigation into lavish spending by other federal agencies, most prominently the General Services Administration.

Court officials responded that such trips have been authorized since 1944 and are used to discuss court business.

But Sessions and Grassley, the top Republicans on the Budget and Judiciary committees, respectively, were not satisfied with the explanation.

"Surely you recognize that the congressional authorization for the circuit's judges to meet and discuss court business is not an invitation to gather annually at the most expensive and far-flung island paradise within the circuit," they wrote. "If it is necessary to amend the statute to reflect that fact, we will work to do so."

Portions of the court's conference, including golf and tennis tournaments and yoga and surfing lessons, will be privately financed. But taxpayers would have to cover airfare, meals and rooms at the Hyatt Regency Maui Resort and Spa, where ocean-view rooms go for $250 a night.

Watchdog groups complained that the trip is wasteful in the face of the nation's staggering debt.

The trip to Hawaii appears to be a tradition for the court. The 9th Circuit met in Maui in 2010 at a cost to the taxpayers of nearly $500,000 just for the hotel accommodations.

The 9th Circuit, which includes seven western states, Alaska and Hawaii, is one of 13 circuit courts nationally. Most of the courts hold conferences similar to the 9th's Maui outing every year or two, though some have cancelled because of budget cutbacks.