What are the consequences for the administration if they just ignore the ruling?
They can be held in contempt and fined. I suppose it’s possible that someone in the administration (but not the president) could be jailed, but I don’t know that has ever happened in US history. If a judge ordered the arrest and confinement of an official, it would fall to the US Marshals to perform that task on behalf of the court. The US Marshals are a part of the Justice Department, which is overseen by the administration. If this were to happen, and the president ordered the justice department to free the official, then we would have a genuine Constitutional crisis in our hands.
I think I'd rather fight insane evil than cold calculating evil. Trump wants to be Putin but Putin has allies and half a brain.