A battle between the U.S. government and a chemical giant revealed a fundamental flaw in the way we control pesticides — one that could be allowing thousands of unsafe chemicals to go undetected.

In a rare show of regulatory muscle, the Environmental Protection Agency (EPA) issued a Notice of Intent on Tuesday, announcing that it planned to cancel the sale of products that included a pesticide called flubendiamide as an active ingredient. The EPA has been monitoring these products, manufactured mainly by the company Bayer CropScience LP (and also by the smaller Japanese company Nichino America, Inc.), over the past few years. Studies have shown the pesticide was breaking down into a different, more deadly compound that was killing mussels and other invertebrates that fish rely on for food — a problem that the agency deemed serious enough to warrant the banning of all products of its kind.

The EPA’s move to ban the products is a novel one, and could signal a change in the way it regulates pesticides, particularly with issuing “conditional registrations,” a loophole that allows pesticides that have not undergone otherwise required safety testing to enter the market. Conditional registrations aren’t uncommon at all — according to a 2013 report released by the Natural Resources Defense Council, as much as 65 percent of more than 16,000 pesticides were first approved by the EPA for the market by way of conditional registrations.