A notable federal version/variation on the Bray case and its significant real-world impact

As we wrap up our mens rea unit with a discussion of "mistakes of law," the Bray case from California demonstrated that certain kinds of "mistakes" about legal issues (about an element of an offense that has a required mens rea) can still matter.  Though Bray is an older case focused on state law decided by a state court, recently the U.S. Supreme Court considered a similar issue in Rehaif v. United States, 139 S. Ct. 2191 (2019).  Here is how Justice Breyer's opinion for the Court in Rehaif gets started:

A federal statute, 18 U.S.C. § 922(g), provides that “[i]t shall be unlawful” for certain individuals to possess firearms. The provision lists nine categories of individuals subject to the prohibition, including felons and aliens who are “illegally or unlawfully in the United States.” Ibid.  A separate provision, §924(a)(2), adds that anyone who “knowingly violates” the first provision shall be fined or imprisoned for up to 10 years. (Emphasis added.)

The question here concerns the scope of the word “knowingly.” Does it mean that the Government must prove that a defendant knew both that he engaged in the relevant conduct (that he possessed a firearm) and also that he fell within the relevant status (that he was a felon, an alien unlawfully in this country, or the like)?  We hold that the word “knowingly” applies both to the defendant’s conduct and to the defendant’s status.  To convict a defendant, the Government therefore must show that the defendant knew he possessed a firearm and also that he knew he had the relevant status when he possessed it.

Can folks see how this federal case is quite similar to Bray?  Also, some might find interesting (but nobody needs to read) this recent law review article discussing Rehaif titled "Does Mens Rea Matter?."  Here is the article's abstract:

Does mens rea matter to the criminal legal system?  Our study addresses this question by performing the first-ever empirical analysis of a culpable mental state’s impact on administration of a criminal statute.  We focus on the U.S. Supreme Court’s 2019 decision in Rehaif v. United States, which applied a culpable knowledge requirement to the federal felon-in-possession statute, 18 U.S.C. § 922(g). 

Prior to Rehaif, federal courts uniformly treated the critical objective element under 922(g) — whether a firearm or ammunition possessor meets the conditions for one of nine prohibited legal categories — as a question of fact for which an actor could be held strictly liable.  Adding a knowledge requirement to this element resulted in a significant decline in the likelihood of a defendant being charged with 922(g), the number of 922(g) charges per defendant, the total number of defendants charged with 922(g), and the total number of 922(g) charges filed each month. 

We estimate that these charging reductions prevented 2,365.32 convictions and eliminated 8,419.06 years of prison sentences for 922(g) violations during the eight-month period following issuance of the Rehaif opinion.  At the same time, prosecutors were just as likely to secure convictions of those they charged with 922(g) after the Rehaif decision as they were before it.  All told, our study suggests that adding culpable mental states to criminal statutes can meaningfully constrain prosecutorial discretion, lower convictions, and reduce punishment without bringing criminal administration to a halt.