Magistrate Thomas Hodgson dismissed the case in in Port Macquarie Local Court which Precision Helicopters, based at Armidale, was being prosecuted by NSW Department of Environment Climate Change and Water for illegal spraying to control noxious weeds at Comboyne.
Michael Fisher owns the 480 hectare cattle farm where the incident was alleged to have taken place.
He was joined in the courtroom by about 20 Mid-North Coast farmers from Barrington Tops to Comboyne.
Mr Fisher said that, despite the dismissal, he was still angry the company had been charged.
"It's a bittersweet win. It was bloody ridiculous to start with. We're bound by law to control our weeds," he said.
The department's arguments had focused on the spraying of weed control Grazon Extra when foliage was wet after rain, which is prohibited.
Lantana, cockspur, tobacco, blackberry and crofton weed are among the weeds he employed Precision Helicopters to control with aerial spraying, Mr Fisher said.
About 30 farmers attended a day of the hearing in September, including Barrington Tops cattle farmer Ted Laurie, 48.
The case began in February.
Mr Fisher said Precision Helicopters' owner and chief pilot, Mark Hodgson, was also glad to have the case dismissed.
"He was pretty relieved it was over and that they got the decision they got," Mr Fisher said.