I was thinking about that coming up. You should take comfort about the fact that in many statutes, this test is used. For example, securities commissions can get involved in a situation and make an order if it's in the public interest. It's not defined, but it hasn't caused them any problems. And there are a lot of statutes at the federal level as well that use the undefined public interest test very well.
On January 30th, 2007. See this statement in context.