The Environmental Protection Agency under the Trump administration is seeking to end a rule that set tougher standards on soot pollution.
The EPA is arguing that the Biden administration did not have the authority to set the rule.
Numerous states sued to block the rule, including Montana, Idaho and Wyoming, which sets higher standards on soot pollutants from tailpipes and smokestacks.
The pollutant is tied to increased risk of stroke, lung cancer and other diseases.
