The court has already ruled in Chevron v. NRDC that executive agencies have deference in interpretation of statues if Congress has not explicitly granted that p

The court has already ruled in Chevron v. NRDC that executive agencies have deference in interpretation of statues if Congress has not explicitly granted that power. The Clean Air act was passed in 1970 to ensure air quality, through science and the advancement of our understanding the EPA has identified CO2 as a toxic pollutant. I don't understand why we need an updated law by Congress when the EPA is much closer to the issue.