Jones refused to talk to WorkSafe New Zealand during the investigation and Carlson admitted that despite owning helmets she didn't wear one because "it becomes just a little bit of a hassle," Mr Barton said.
"WorkSafe warned the couple, then issued a prohibition notice which was ignored," he said.
"This behaviour does not represent the sensible approach taken by most farmers to quad safety, but as a regulator, we could not ignore this wilful refusal to meet their legal obligations."
Quad bikes posed a serious risk on farms, Mr Barton said. On average, five people were killed and 850 were injured every year.
The best way to stay safe on a quad bike was to always wear a helmet, never let kids ride adult quad bikes and to choose the right vehicle for the job and get proper training, he said.
Federated Farmers health and safety spokeswoman Katie Milne said the court case and ruling ran the risk of alienating farmers who would see the fines as heavy handed and excessive.
"This sort of public issue is just going to get farmers' backs up and make them feel picked on -- not make them safer farm operators, which is what we want."
She said the focus should be on outcomes, increased awareness and changing behaviour.
"No one wants to see serious accidents and deaths. We need good information and evidence in the public domain that not only drives the identification of major health and safety risks, but subsequently the priorities, education and persuasion to change behaviour."
Federated Farmers had been working closely with WorkSafe NZ to improve farm safety, Ms Milne said.
"WorkSafe have been saying to us that they want to avoid heavy handed actions and put a high value on education and persuasion. "We will be talking to them about how this is done more effectively."
More information on quad bike safety can be found at: www.business.govt.nz