Let's say I don't know any better, that the case is about public display of the ten commandments instead of state rights vs. federal government. So if the Supreme Court rules that public display of the ten commendments is effectively the establishment of a national religion (which I don't see how because all mainline Protestant, Judaism and Islam faith revere them, which one is it that is being established?) then they have to remove the ten commendments that are edged in stone above their heads (the justices) in the court room where they hear cases. If Congress step in and withhold all funding for that purpose (the same way they withhold funding for any federal marshall to enforce the federal district court's decision in Alabama), what will the justices do?

No where in the US Constitution is the expressed phrase of separation of church and state is found. The only thing that is not allowed by the establishment clause of the first amendment to the US Constitution is for Congress to pass a law saying that the USA national religion is Episcopal or Baptist or whatever. The letter from Thomas Jefferson to the Danbury baptist church is to assure them of this.