It's a little bit broader than this. In the Fed there is the so called "statutory price for gold" and it's not limited to gold certificates. Any gold in the Fed would be priced at $42 by law. The fact that they don't technically own any gold and work around the issue only makes it so much more amusing. It only serves to tell people they can fix prices and make outrageous course-correction changes overnight and people will still argue "it's fine and it's legal" afterwards.
https://www.federalreserve.gov/data/intlsumm/current.htm