Make no mistake: Amendment 74 is a big deal.

The initiative would amend the Colorado constitution to give property rights owners significantly more power to sue government for policy or regulation that they think devalues their property.

Proponents say the law is intentionally vague and a way to force the Colorado Supreme Court to further clarify already broad protections for property owners against government influence. Critics, including Aurora Mayor Bob LeGare, say the amendment would open the floodgates for a wave of litigation against virtually any act of state or local government, from zoning and affordable housing to public works and environmental regulation.

Amendment 74 is backed by oil and gas interests, which have invested heavily through a series of advocacy groups.

Amendment 74, would require government to compensate property owners for regulation that reduces the “fair market value” of their property.

Colorado has existing protections for property owners. The Fifth Amendment to the Constitution prohibits government taking property without just compensation, like buying and demolishing houses to expand a freeway. Further, the Colorado constitution mandates government to compensate residents for damages to property.

But a common criticism of the status quo is that eminent domain payouts tend to be too low for property owners.

Amendment 74 would add reduction in “fair market value by government law or regulation” to those protections.

What would constitute “fair market value” is up to the courts to decide, said Shawn Martini, Vice President of Advocacy at the Colorado Farm Bureau, which is sponsoring Amendment 74.

Both sides of the issue agree that the vague language in the amendment would make work for lawyers in Colorado courts as the meaning of the amendment is fleshed out.

He said the amendment would be a legal argument for property owners to challenge government overreach.

“Anybody who owns property in the state of Colorado could potentially benefit if a government does something that is punitive,” Martini said.

Martini said the Amendment stems from a 2001 case heard by the Supreme Court in which La Plata County prohibited mining on part of mining company’s land to protect a nearby river. The mining company sued the county to be compensated for the lost economic value of the land, but lost the case.

Sam Mamet, Executive Director of the Colorado Municipal League, said cities, counties and the state government could be sued by property owners for just about any action, from routine zoning to statutes limiting liquor stores from nearby schools.

“All it is gonna take is one property owner who says, rightly or wrongly, I’m not complying, and if you force me too, I’m gonna argue that the action reduces the value of my property – and I’ll see you in court,” Mamet said. “This is the single worst ballot measure I’ve ever seen, ever, on the ballot.”

Mayor of Aurora Bob LeGare said city-approved projects like Providence at the Heights, a would-be residence for disabled Aurorans experiencing homelessness, could be challenged by residents concerned that nearby property would depreciated in value.

“If it was focused on farms and mineral rights, I wouldn’t have a problem with it,” LeGare said, “but it affects everything and anything we do in the city of Aurora.”

Amendment 74 is also backed by the Committee for Colorado’s Shared Heritage, a group funded almost entirely by Protect Colorado, an advocacy group for the oil and gas industry.

Protect Colorado has contributed over three million dollars to Colorado’s Shared Heritage, according to October 1 campaign filings.

“It’s a good measure, discussed in Colorado for years,” said Karen Crummy, a spokesperson for Protect Colorado.

Martini, the Colorado Farm Bureau spokesperson, said oil and gas interests had a role in drafting the amendment and the campaign.

“We’re a campaign and campaigns are expensive,” he said. “Farmers aren’t the richest people in the world.”

Attorney General candidates Phil Weiser and George Brauchler both acknowledge the amendment could have an outsized impact on the attorney general’s office, which provides legal counsel for governments and state government agencies.