A confusing proposal to reform the 'mens rea' of federal criminal law

The New York Times reports on a bill recently introduced by Rep. James Sensenbrenner (R-Wis.) that includes the following global reform on the mental states (what criminal law types call "mens rea") of federal criminal laws:

§ 11. Default state of mind proof requirement in Federal criminal cases

If no state of mind is required by law for a Federal criminal offense-
(1) the state of mind the Government must prove is knowing; and
(2) if the offense consists of conduct that a reasonable person in the same or similar circumstances would not know, or would not have reason to believe, was unlawful, the Government must prove that the defendant knew, or had reason to believe, the conduct was unlawful.

According to the Times, libertarian groups endorse this reform but the Obama administration opposes it. The Times suggests that it might go through despite Obama administration opposition, at least in some form, because it may end of as part of a broader package of criminal justice reforms.

I hadn't heard of this mens rea proposal until the Times article, but reading over it, it strikes me as confusing. Putting aside whether it is a good idea or a bad idea—and I'm skeptical about it, because global solutions like this often have major unintended consequences—I have a lot of questions about what it means and how it's supposed to work.

Let's start with the first part, that "if no state of mind is required by law for a Federal criminal offense," then "the state of mind the Government must prove is knowing."

First, what is "required by law"? Does "required by law" mean "expressly written into the text," or does that mean "required by the statute as interpreted by judicial precedent"? Let's say that a statute has no express mental state, but the Supreme Court has said that the required mental state is intent. Does this new provision trump the Supreme Court, lowering the mental state back down to knowing? Or does the precedent still apply? If precedents still apply, what if the precedents are lower court cases that have not been uniformly adopted? Would a court follow the precedent where it is binding but not where it isn't, leading to different interpretations of the law? And if that happened, what standard of "required by law" would the Supreme Court use to resolve the differences?

Second, does the requirement that "no state of mind is required by law for a Federal criminal offense" apply to every element, or just one element? Crimes consist of several elements, and each element of the crime has a mental state. Is the law supposed to be triggered only when Congress (or judicial precedent, see above) has not included any mental state, or when there is no express law on the element for that particular element? For example, imagine Congress passes a law prohibiting "sending a violent threat with the intent to use a means of interstate commerce." If a court is trying to figure out the mental state required for a threat, does the new statute apply because Congress did not include a mental state for that element, or does the statute not apply because Congress included a state of mind for a different element?

Now turn to the second part. It says that "if the offense consists of conduct that a reasonable person in the same or similar circumstances would not know, or would not have reason to believe, was unlawful, the Government must prove that the defendant knew, or had reason to believe, the conduct was unlawful." Notably, it is not expressed as a global new element of the offense that the government would have to prove every time. Instead, it's expressed as a conditional. If a set of facts exists—"a reasonable person in the same or similar circumstances would not know, or would not have reason to believe, [the conduct] was unlawful"—then the government has an added burden—"the Government must prove that the defendant knew, or had reason to believe, the conduct was unlawful."

First, how would that work? Can the defense put evidence of this before the jury without prior judicial authorization, or would the defense need to make a proffer to the court, and get the judge's authorization, before doing so? Either way, what's the relevant evidence a jury would hear about what a reasonable person would think about the law? Importantly, the standard is objective: It's whether "a reasonable person" who committed the (alleged?) offense wouldn't have reason to believe the offense was unlawful. Does this mean that the defense can put on legal experts to testify about the state of the law, or maybe present a poll about what people think is legal or illegal?

Second, how much is enough to have a "reason to believe" that conduct is unlawful? A person might know that there are vague laws out there, and that there is uncertainty about what they cover. Is that enough to provide a "reason to believe"? Does that mean "a little bit of a reason," or "a really good reason," or something else? Imagine the defendant asked a lawyer who said that the conduct was probably legal. Does that mean that the defendant can't invoke the defense (because he had enough reason to believe that he asked for legal advice) or that he can (because the lawyer said he was probably okay)? Also, what does "unlawful" mean in this context? Does "unlawful" mean a tort? A regulatory violation? Only a crime?

Third, who is the group of people "in the same or similar circumstances" as the defendant? Imagine the defendant asked a lawyer for advice beforehand and the lawyer said the act was probably okay. Is the group of similarly situated reasonable people those who did the act? Or is it those who did the act and sought legal advice? Or is it those who did the act, sought legal advice, and were told by counsel that the act was probably legal? What if the defendant carefully picked a lawyer who he expected would say that the conduct was probably legal—does that become part of the "similar circumstances," too? How narrowly or broadly to construe objective tests is a recurring problem in criminal law, but here the wrinkle of assessing legal knowledge and risk strikes me as raising extra difficulties.