The public debate over Proposition 98 has centered primarily on rent control and eminent domain, but aspects of the law would also impair the ability of local governments to regulate development, whether to preserve endangered species or ocean views, opponents say.

"If this measure were to pass, it would roll back our environmental and community protections at least a generation," said Jeremy Madsen, executive director of Greenbelt Alliance, a San Francisco land-use planning group. "It would invalidate planning, zoning and other regulations that are put in place by local governments to enhance the quality of life."

Jon Coupal, president of the Sacramento sponsor of Prop. 98, the Howard Jarvis Taxpayers Association, shot back that opponents of the measure have invented the contention that it would hamstring government's ability to oversee development.

"It's classic fearmongering," he said. "They also claim it will contribute to global warming. It's the kitchen sink."

The truth between the positions turns principally on a clause in the proposed law defining restrictions on "private use" to include regulating "real property or associated property rights in order to transfer an economic benefit to one or more private persons at the expense of the property owner."

Critics say that means cities or counties could be sued every time they approve, deny or change a project in a way that prevents a single property owner from realizing the full potential economic value of their holdings, even if the ruling is done for the sake of public safety, the environment or neighborhood character.

Other language in the law could invalidate requirements that a certain portion of units in a project be set aside as affordable, which is common in many Bay Area cities, and restrict the use of eminent domain for public water projects, they say.

"It would severely undermine the ability of communities to make decisions about how they want to grow and change," said Vivian Kahn of the California Chapter of the American Planning Association.

Coupal dismissed such claims, emphasizing the "in order to" phrase in the clause in question. That means the government agency's ability to regulate is limited only when its primary motivation is to transfer economic benefit, not when it's a side effect to a decision motivated by public safety concerns, he said.

The real intent of the law, he and other supporters say, is to prevent the government from using eminent domain in a way that allows anyone to profit from the taking of private property.

"We don't want the government or anyone else having the power to force any private citizen into a transaction," said James Kilpatrick, president of the Berkeley Property Owners Association, a landlord trade group supporting Prop. 98.

If that were truly the entire objective, it would have been spelled out much more clearly, said Dean Preston, executive director of San Francisco advocacy group Tenants Together.

"It doesn't say 'prime motivation,' and I can guarantee if Prop. 98 passes, Coupal and his landlord supporters will be going to court making the exact opposite argument," he said.