The Unity-based Maine Organic Farmers and Gardeners Association is among 15 organic-food advocates nationwide that have sued the federal government over rule changes governing how non-organic substances are certified for use in organic farming.

The suit, filed in Federal District Court for the Northern District of California, according to The New York Times, contends that the U.S. Department of Agriculture violated rule-making procedures by failing to hold a public hearing or seek public comment when it changed the rules.

Under the old rule, non-organic substances were reviewed every five years for potential hazards and to determine if they were still needed. Now, the automatic review has been eliminated, and substances stay on the “allowed” list unless there is a specific vote by the National Organic Standards Board to remove them.

The suit is asking the court to force the department to abandon the new rule, established in 2013, and reinstate the traditional public hearing and comment process.

The organic groups – representing a $35 billion market in the U.S. – claim the policy change “violates the foundation principles and practices” of the Organic Foods and Production Act of 1990.

The measure set standards for organic certification and established the National Organic Standards Board to oversee which synthetic materials are to allow for use in organic farming. The board determines whether the synthetic substances would harm health or the environment, and whether there is a non-synthetic alternative available, according to a MOFGA release.

MOFGA Executive Director Ted Quaday could not be reached for comment Wednesday.

Organic producers maintain that the old public process led to public trust in the USDA organic label. As a result, they say, there has been enormous growth in organic sales over the past two decades.

The plaintiffs say there should be “an open and fair decision making process, subject to public input.” Legally, they said, the agency’s decision represents a rule change and therefore must be subject to public comment, according to the statement.

“But equally important, it is a departure from the public process that we have built as a community,” members wrote. “If we do not hold the line on public process, we fear that in decision after decision, organic will lose its meaning.”