So, USPTO grants an invalid patent, and patent troll uses it to shake down whoever they wish? I surely think it's illegal. If there is no law which makes it so, there should be one. I'd say even if the patent is valid, one can't use shakedown methods like "pay up or else".

Patent trolls even big ones like Microsoft for example use intimidation to squeeze money. Their tactic is clearly to use high cost of litigation to force everyone to settle outside of court. I.e. it can go like this. A troll comes to some company and says: "Nice business you have here, it would be a pity if anything happens to it. Pay up or else". Company answers: "We'll fight to invalidate your patents". Troll says: "So what, we have tons more we can pull out, you don't have money to fight to invalidate them all, so better pay up". Whether they are valid or not such practice should be illegal because it's not any different than criminal shakedown.

>It sounds like you don't like what you see, and you want to find something in the law to use against them.

Indeed. I'd prefer them to be persecuted as racketeers, because they are such. I agree that if the law doesn't cover such case it should be fixed.

If the patent was invalid for reasons known to the people threatening action, then I think it's reasonable to at least be called fraud. If they were (or might've been) operating under the belief that the patent was legit - and certainly granting by the USPTO would dispose one to this belief, if there wasn't some reason they knew better - then I think it's as you say.