One of my law profs noted that a big chunk of law-as-a-reality depends on the burden of proof. Since most things in the world are utlimately unprovable, whoever has the burden has a hill to climb.

So yesterday, at a Federalist Society conference, I was able to ask some of the nation's finest professors and experts on IP the crucial question about injunctions under the eBay decision: Who has the burden of proof?

Clearly, the patent holder must prove infringement. But what about the "four factors" -- (1) Existence of irreparable injury; (2) Remedies at law are not adequate; (3) Balance of hardships favors the plaintiff; (4) An injunction would not disserve the public interest?

Their answer was: Who knows? This is equity, so it's loose, and the ultimate issue is at the discretion of the trial judge, who can assign the burden pretty much as he/she chooses, subject only to reversal for abuse of discretion.

This is an unfortunate state of affairs. I take it the Roberts opinion would give the patent holder a presumption on all of these issues, putting the burden on the infringer to come forward, which would be the best solution. I don't think the majority opinion or the Kennedy concurrence contradicts this view of the proper allocation of the burden; they just do not address it.

Now, there is no way to get to such a rule without years of litigation. If Congress is doing patent reform, it should consider tossing this into the mix.