They do but under a textualist/originalist viewpoint. There is literally a clause in the Constitution stating that state legislatures set election laws, not the courts like what the PASC did. This is why I think PA is going to be a relatively easy win for Trump since the law they changed extended the time to turn in mail-ins from e stated) 8 PM the day of election (as the PA legislature set) to 3 days after the election. Also, Justice Alito told the PA Elections Board to seperate the late main-ins from the rest of them, which they promptly ignored.