From your link:

> the practice can increase nitrogen oxide emissions as much as 310 times, non-methane hydrocarbons 1,400 times, and carbon monoxide 120 times

Note that at least one of the men, Jonathan Achtemeier, was caught doing much more than "rolling coal" himself. He led a nationwide conspiracy to "roll coal", charging money to help hundreds of people do it although he knew it was a crime. Career criminals like Mr. Achtemeier rarely stop when they get caught the first time.

If you assume, hypothetically, that the justice system is operating as it should, a pardon means giving one person the right to ignore the laws of the country for a select few acquaintances.

If one has to tolerate this blatant avenue for favoritism, I’d rather see the Supreme Court or judges themselves invested with this power, rather than the president.

I guess I am biased by believing in the separation of the executive and judiciary powers.