Question about possible legal challenge in Pa.

I just saw this exchange in the comments of the New York Times. I also am not a lawyer, but an 18 year old pre-med student. Is this accurate?

Comment

"Doesn't Marbury v. Madison mean that Courts can overrule legislatures? So, isn't it wrong when "Justice Kavanaugh also said that state legislatures, rather than state courts, have the last word in setting state election procedures"? I'm sure we can come up with bigoted legislatures coming up with a new law that disregarded the State's Constitution and maybe even the US Constitution. In those cases, the State Court could overturn the legislature. (I am not a lawyer.)"

Response to Comment

"The issue in Pa. is that the state supreme court ruled on state (not federal) constitutional grounds that mail-in votes must be counted if postmarked before or on election day. The state legislature did not pass a law to that effect. So, the argument would be that the state SC usurped the state legislature's US constitutional mandate. I hate to say it, but this looks like an easy case on the face of things. I believe Trump would win the case. Let's hope Biden doesn't need Pa."