Conservatives who have spent decades asking the Supreme Court to rein in the US government’s regulation of businesses are now betting on a case involving fishermen challenging a $710 fee they’ve never had to pay.

The case could undercut the power of federal regulators on major issues including air pollution and securities fraud. It also exemplifies the way many of the high court’s biggest fights are born these days — driven less by the practical aims of the litigants than by the ideological vision of the interest groups behind the suits.

The fight concerns a federal requirement that some herring boats host government-approved observers aboard their vessels and cover an estimated $710 daily cost. The fisherman say that would be an onerous burden on their family-owned businesses — so onerous they are suing even though the fee is on hold and might never kick in.

“We have not had to pay. We’re just nervous about this hanging over our head,” said Bill Bright in an interview in Cape May, New Jersey, where he runs his two-vessel fishing business. “So we feel that we need to solve this problem now.”

The real stakes lie in the broader legal issue, one that anti-regulatory groups have eagerly sought to get before the Supreme Court and its conservative supermajority. The justices are considering overturning a 1984 ruling known as Chevron v. Natural Resources Defense Council, under which judges typically defer to regulators on the meaning of ambiguous statutes – including those that set out how much power the agency has.

Democratic administrations have relied heavily on the so-called Chevron doctrine, using it to justify rules governing energy, the environment and the workplace. In the herring case, a federal appeals court invoked Chevron in upholding the National Marine Fisheries Service’s payment demand even though Congress didn’t explicitly authorize the rule.

“At stake is a foundational legal principle that our nation depends on to protect millions of people from climate pollution, consumer fraud and destruction of our fisheries,” said Vickie Patton, general counsel of the Environmental Defense Fund.

Critics of the Chevron decision have filed dozens of briefs urging that it be overruled or at least scaled back. The US Chamber of Commerce told the justices the Chevron doctrine “has contributed to an unpredictable, unstable regulatory environment.”

The justices will hear arguments in January in two near-identical cases, each being pressed by a group funded by conservative billionaire Charles Koch’s network. The New Jersey case is being spearheaded by the Cause of Action Institute, which lost on procedural grounds when it filed a similar suit eight years ago over industry-funded monitors for other species of fish.

Advocates on both sides say the legal issue before the court is an important one for the fishing business. The key question is whether Congress authorized the Fisheries Service to impose monitoring charges on herring vessels. The agency is relying on a provision that says it can take steps that are “necessary and appropriate” to prevent overfishing, rebuild stocks and promote the long-term health of fisheries.

Critics say an expansive reading of that provision would leave fishing businesses vulnerable to crushing fees. “Once they’ve got it fixed in the legal firmament, they can go charge whatever they want,” said John Vecchione, a lawyer with the New Civil Liberties Alliance representing a separate group of fishing businesses in New England.

Environmentalists contend the long-term health of the oceans depends on a Fisheries Service with enough power to ensure it gets the information it needs.