SCOTUS ruled that CO2 was a pollutant in 2007, in the case of Massachusetts vs EPA. It was a 5-4 decision with Kennedy voting with the 4 dems.
Additionally, SCOTUS said that EPA should determine the risk that CO2 played, which would be called the Endangerment Findings, and if needed EPA should use the Clean Air Act to regulate CO2, which means EPA needs nothing from congress.
Back in those days everyone said it would be better for congress to preempt EPA, which was called the House Cap and Trade bill, but after that failed, in 2010, Obama would move forward with EPA regulating.
Obama's first set of CO2 regs dealt with new permits only, which generated many lawsuits in 2010. That had to go all the way back to SCOTUS who ruled for Obama in 2014.
Also in 2014, Obama would issue his second set of regs, that deals with existing permits, which was/is called the Clean Power Plan. This set off another round of lawsuits. The DC Court of Appeals has heard the case and is supposed to rule on the case in Feb. After which, if they get a 9th on SCOTUS, it can be appealed to SCOTUS.
The SCOTUS needs to hear this case again.
Uh...Chemistry nor Science are subject to legal debate.
A court declaring CO2 a pollutant is nonsense.