That includes bills passed by an earlier Congress and signed into law by previous administrations.
Sounds like a rotten job, actually. I could never be a lawyer forced to take a position that I was fundamentally opposed to.
I had wondered whether that was the case. You're right, it would seem to be peculiar in a lot of circumstances. Can you see Abraham Lincoln's Solicitor General standing up and arguing the cogency of the Fugitive Slave Act to the Supreme Court, with Roger Taney sitting up there on the bench? It would be very odd.