They can’t rule contrary to the Constitution, but their job is to interpret what it says. Why do you think that the confirmation process gets so ugly? Politicians try to pick people for the Court who they feel will interpret the Constitution to their liking because they either don’t have the votes or the political spine to change the law in the legislature. It is politically easier to attempt to stack the Court in your favor than to follow the Constitution and have the legislative branch pass or change our laws. Just look at the headlines today. It is all about each side either demanding or worried that the Court will overturn Roe or invalidate the 2nd Amendment.