When the Supreme Court Can Move Markets

Supreme Court opinions rarely move markets. I don't know enough about the Court's great antitrust opinions to know if they did, though they probably did for individual stocks. (John D. Rockefeller's response to the Court's opinion upholding the breakup of Standard Oil was "Buy Standard Oil," which was good advice.)

But can you can imagine a future Supreme Court decision on the legality of tariffs moving markets. And this creates some special concerns that people should start thinking about: For example:

1. Sometimes Supreme Court deliberations or opinions leak out. The opportunities for insider trading are obvious. Let's hope that the Court's security is better and that the insider trading laws clearly apply to the use of confidential court information. (I have no idea on the latter.)
2. The Court usually issues merits opinions at 10AM on a weekday. Right during stock market trading. Maybe this is a bad idea for a market-moving opinion.
3. Maybe #2 means that the Court should say in advance when the market-moving opinion is coming by issuing a special 4PM release time. In 1935, the Court did telegraph the day when it's opinions in the Gold Clause Cases would come out to squelch market rumors that it would be some other day, though they did not change the release time.
4. Deciding such a case on the emergency docket is not good because oral argument can at least signal where the Court is going and cushion the blow.