Serious people don't do pro-bono work to advance bad constitutional law. Pro-bono is volunteer, for free, time that you contribute because it is a good thing to do. Yes, but Roberts did not take on the pro-bono work, the firm he worked for did. Roberts did not argue or write briefs, he simply reviewed briefs as a favor to his firm.
Roberts did not take on the pro-bono work, the firm he worked for did."""
He wasn't obliged to participate.