[Ken H]

If Congress removes jurisdiction from the federal courts, what court are they going to challenge it in?

Congress could create a special court to deal with marriage and they could limit appellate review of that court by the USSC.

However, Congress cannot shield their acts from some form of judicial review.

[inquest]

Congress could create a special court to deal with marriage

Why would they need to do even that? All they would have to do is remove from all federal courts the power to deal with matters of same-sex marriage. Problem solved.