Two sides of a proposed corporate sales tax on the November ballot are clashing over a fundamental tenet of the measure — how the revenue can be spent.

Initiative Petition 28 — which is on track to be called Measure 97 on the ballot — would levy a 2.5 percent tax on certain corporations’ Oregon sales exceeding $25 million.

Our Oregon, the nonprofit group backing the proposal, wrote in Section 3 of the initiative that revenue from the tax “shall be used to provide additional funding for public early childhood and kindergarten through 12th grade education, health care and services for senior citizens.”

Opponents of the measure argue that passing the tax is akin to writing a “blank check” to the state Legislature, because the ballot measure is not constitutionally binding.

That means that lawmakers may spend the estimated $3 billion in annual state revenue from the tax for any purpose they see fit.

An opinion released Monday by the nonpartisan Office of the Legislative Counsel supports the opponents’ claim.

“Section 3 would not bind a future legislature in its spending decisions,” wrote Chief Legislative Counsel Dexter Johnson in the opinion issued to Rep. John Davis, R-Wilsonville. “If Measure 97 becomes law, the Legislative Assembly may appropriate revenues generated by the measure in any way it chooses.”

Only a constitutional amendment could restrict how the Legislature spends the money, legislative counsel concluded.

Katherine Driessen, a spokeswoman for Our Oregon, said the ballot measure “spells out very clearly where the revenue must go.”

“As with any law, the Legislature would have to change the law in order to spend the money on anything else,” Driessen said. “We believe that with the billions needed to boost our schools and critical services, any Legislature would be hard-pressed to spend the money on anything other than those areas.”

Sen. Richard Devlin, D-Tualatin, co-chairman of the joint legislative Committee on Ways and Means, said going against voters’ wishes would stir up political backlash.

“They could use it (IP 28 revenue) for anything they want at their own peril,” Devlin said. “If it passes, the voters would have spoken very clearly that they want these things improved.”

The Legislature has modified ballot measures in the past to fix sections that didn’t work or to add clarity, but generally has adhered to the intent of such laws, Devlin said.

For example, lawmakers have made several tweaks to Measure 91 legalizing recreational marijuana since voters approved the law in 2014.

“Obviously you’ll run into some marijuana advocates who’ll say we didn’t follow what they’d hoped for, and you’ll probably run into some people who weren’t advocates who said we went too far, but I think the Legislature actually tried” to follow the spirit of the law, Devlin said.

Proponents of the measure and lawmakers already disagree on interpretations of the intent of Measure 97.

Lawmakers on the ways and means committee have said some of the revenue from Measure 97 could be used to help offset some $885 million in projected cost increases to the state’s public pension program, known as the Public Employees Retirement System.

“It could be used for reserves or PERS, if it’s needed to,” said Rep. Peter Buckley, D-Ashland, who co-chairs the committee with Devlin.

Driessen, Our Oregon spokeswoman, said using Measure 97 revenue for PERS would conflict with the intent of the initiative.

But lawmakers say that view denies the reality that PERS is part of the budgets for K-12, health care and senior services.

“I could put a certain amount into K-12 and say I’m not covering the PERS funds then the school districts don’t have that much in additional resources because they do have cover the PERS costs, so it isn’t like there is a barrier between these two,” Devlin said.

Lawmakers also want to have the flexibility to repurpose revenue in the event of an economic downturn or other financial crisis, in order to avert layoffs or cuts in basic services, Buckley said.

“You’re going to get this from both sides,” Devlin said of the battle over IP 28. “One side is going to say the Legislature can do whatever they want with this so then you shouldn’t approve the measure. The other side is going to say: Voter, you’re going to get everything you ever wanted if you vote for the measure.”