North Dakota Senate advocates of squirreling away some of the state's oil tax revenues have prevailed over lawmakers who believe a special fund is not necessary for the Legislature to save money.

Senators on Thursday endorsed a constitutional amendment that would establish the oil tax savings fund and require approval of three-fourths of the state House and Senate to dip into the fund's principal. Twenty-four senators supported the amendment, the minimum needed, while 21 opposed it.

"I think we all know what it's like to put a cookie jar on the counter and watch the cookies disappear," said Sen. Dwight Cook, R-Mandan. "When you find times like that, you've got to put the cookie jar up a few shelves, and that's all we're doing. We're raising the cookie jar."

Sens. Judy Lee, R-West Fargo, and Joel Heitkamp, D-Hankinson, were among the lawmakers who argued the amendment would limit the Legislature's future options because of its super-majority requirement for using the oil tax fund's principal.

"I think there's a hint of arrogance on our part when we're suggesting that we know better than any future legislative body … what should be done," Lee said. "And so we're going to make it really, really hard for anybody to make these changes in the future."

Heitkamp said if lawmakers want to set aside money in reserve, they can already do so.

"We have the power … to do any of this," Heitkamp said. "What this is about is locking up the people who come behind us."

The amendment now returns to the North Dakota House, which voted 87-3 earlier this month to approve a different version. Representatives will have to decide whether to endorse the Senate's changes, or ask for a conference committee to work out a final version of the measure.

North Dakota constitutional amendments must be approved by voters to take effect. If the Legislature agrees to put the measure on the ballot, it will get its vote during the November 2008 general election.

The amendment says that once North Dakota's oil and gas tax collections exceed $100 million during any two-year state budget period, any surplus goes into a "permanent oil tax trust fund." The $100 million threshold would be adjusted every two years to account for inflation.

The fund's interest earnings would be transferred to the state treasury every June 30, when the budget period for North Dakota government ends.

Its principal could not be spent unless three-fourths of the House and Senate agreed to do so. The amendment says no more than 20 percent of the principal may be spent during any two years.

During the current biennium, North Dakota is expecting to collect $158.5 million in oil extraction and production taxes. Forecasters say the sum should rise to $167 million during the 2007-09 budget period.

If the amendment were in effect now, it would require state budget writers to transfer $58.5 million into the oil tax fund during the current budget cycle, which ends June 30. The transfer amount would rise to $67 million in the next two years. The resolution is HCR3045.