The Association of American Railroads (AAR) filed a lawsuit June 16 against the California Air Resources Board (CARB) over the In-Use Locomotive regulation.

In the suit, the AAR and the American Short Line and Regional Railroad Association (ASLRRA) claim that CARB doesn’t have the legal authority to promote the In-Use Locomotive rule, which would introduce many new measures, including one that would require train operators to pay money into a state spending account based on their emissions levels in California.

In a statement, the AAR said it was filing the lawsuit because the rule “would limit the useful life of today’s locomotive fleet (over 25,000 locomotives) and mandate their premature replacement with zero-emissions locomotives.”

“This [zero-emissions] technology has not been sufficiently tested in prototype or operational service and is not commercially available on the market today,” the AAR wrote in the June 16 lawsuit announcement. “In the past, railroads have worked with CARB to further initiatives that have dramatically enhanced air quality surrounding operations in the state and helped pave the way for more sustainable operations across the nation.”

“While the urgency to act is real and unquestionable, CARB uses unreasonable, flawed assumptions to support a rule that will not result in emissions reductions,” said AAR president and CEO Ian Jefferies. “Railroads are working toward reliable, efficient zero-emissions technologies; however, they cannot simply be willed into immediate existence by policymakers.”

As part of the lawsuit, the AAR and ASLRRA asked that the rule not be implemented or enforced while California district courts consider the case.