The "crime" = "action" + "state of mind" conceptualization is the result of the Model Penal Code (http://en.wikipedia.org/wiki/Model_Penal_Code), which is an extremely well thought-out systematization of the centuries old principles of Anglo-American penal law.

Ango-American law has always placed a very heavy emphasis on state of mind, though the Model Penal Code is more rigorous about applying the principle. However, it stops far short of punishing thought crimes, because it always requires a guilty state of mind to be accompanied by action.

As for why this is rational, think deeply about the attempted murder example. Consider A plots to murder B, and with that plot in mind buys a gun and heads for B's house. The police catch him and charge him with attempted murder because: 1) he intended to kill B; 2) he took a substantial step towards carrying out his goal. Why do we punish A? Nobody has actually gotten hurt, and B might not even know he was in danger. Moreover, say A unknowingly bought a defective gun that wouldn't shoot. Is he still guilty of attempted murder? Yep. Why? Because he had the required guilty state of mind but not only that he took action while having that guilty state of mind. We don't punish the state of mind by itself, we punish the convergence of guilty state of mind and action.

In this case, the people: 1) intended to smuggle illegally-taken lobster tails; and 2) actually imported the tails. The secret code they used and their failures to report are evidence that they knew or believed they were engaging in illegal activity. Should we punish them? Why not? How is this situation any different? The fact that the tails are legal under Honduran law is merely a fact like the inoperable gun in the previous example.

Even granting applicability of mens rea / actus reus analysis here, I believe your analysis is wrong. It's true that attempting to do something actually illegal and failing is often still an offense (usually of the "attempted" variety), but incorrectly believing that what you intend to do is a crime, when it actually isn't, does not automatically make that act criminal. For example, if you think jaywalking is a crime in a jurisdiction where there is no law against it, that will not in itself render your jaywalking criminal. That would be an absurd result.

Kaffee: It was oregano, Dave. It was 10 dollars worth of oregano. Lieutenant Dave Spradling: Yeah, but your client thought it was marijuana. Kaffee: My client's a moron that's not against the law. Lieutenant Dave Spradling: Kaffee, I have people to answer to just like you do. I'm going to charge him. Kaffee: With what? Possession of a condiment?

Your interpretation of mens rea is just way off. If I'm driving a propeller boat, and I kill a scuba diver that forgot to post the bouy signalling his presence, then I haven't commited a crime, because I was unaware, and could not reasonably be aware, that there was a scuba diver under my boat.

On the other hand, if there is a bouy, and I drive over the top without killing the diver, and it can be demonstrated that I was intending to harm the diver then yes, I can be convicted for attempted murder. Attempted murder mind you, and not murder itself. This requires that attempted murder be a crime. Back to our erstwhile smugglers, if there is a crime of attempted smuggling then yes, they should go down for it, as they were indeed attempting to smuggle. If the only crime on the books is actual smuggling, then they should waltz out of the courtroom.

I disagree, largely based on the severity of the attempted "crime." Sneakily importing lobster tails that turn out to be legal is more akin to deliberately driving 75 in what you think is a 65 zone, but actually turns out to be an 80 zone (yes, they do exist). Doing so is not worthy of a speeding ticket.