A court-imposed condition requiring a mining company to purchase an elderly farmer's property before going ahead with an open-cut coal mine has been described as a "poison pill" by the company's lawyers.

Chinese-owned Yancoal is appealing against a ruling in the Land and Environment Court that said its Ashton South East open-cut coal project could only proceed if the company acquired the property of Wendy Bowman, a farmer in her eighties who has refused to sell.

Bret Walker SC told today's hearing that the condition made no sense.

"Why would you apply this poison pill, that flies in the face of the approval process?" he said.

"This is a condition that prevents us from doing anything at all."

Mr Walker said the company would be breaking the law if it moved to commence work on the project.

But counsel for the Hunter Environment Lobby Robert White said there was nothing remotely irrational about the ruling.

"The condition creates certainty that the project [the judge] environmentally assessed, would be carried out," he said.

Wendy Bowman did not attend the hearing, but said in a statement: "We need to keep food-growing soils in Australia, not dig them up for coal."

"I will not be selling, regardless of the appeal outcome."

Speaking outside court ahead of the hearing Hunter Environment Lobby president Jan Davis said the community was being "shafted" by mining interests.

"They don't really care about people like Wendy Bowman," she said.

"Once you've dug up beautiful farming areas, they're lost forever."

The NSW Court of Appeal reserved its decision.