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Page Number: 8.0

4 

XIULU RUAN v. UNITED STATES 

Opinion of the Court 

709 F. 3d 1082, 1097 (CA11 2013); emphasis added; altera-
tion in original). 

Kahn’s  trial  contained  similar  disagreements  over  the 
proper  mens  rea  instructions.    Ultimately,  the  District
Court  instructed  the  jury  that  it  should  not  convict  if  it 
found  that  Kahn  acted  in  “good  faith,”  defined  as  “an  at-
tempt to act in accordance with  what a reasonable physi-
cian  should  believe  to  be  proper  medical  practice.”    App. 
486.  The court added that to find “good faith,” the jury must 
conclude that Kahn “acted in an honest effort to prescribe
for patients’ medical conditions in accordance  with gener-
ally recognized and accepted standards of practice.”  Ibid. 
The court also told the jury that “good faith” was a “com-
plete defense” because it “would be inconsistent with know-
ingly and intentionally distributing and/or dispensing con-
trolled substances outside the usual course of professional 
practice and without a legitimate medical purpose.”  Ibid. 
The jury convicted Kahn of the §841 charges, and he was
sentenced to 25 years in prison.

The Tenth Circuit affirmed Kahn’s convictions.  See 989 
F. 3d 806, 812, 824–826 (2021).  In doing so, the court held 
that  to  convict  under  §841,  the  Government  must  prove
that  a  doctor  “either:  (1)  subjectively  knew  a  prescription 
was issued not for a legitimate medical purpose; or (2) is-
sued  a  prescription  that  was  objectively  not  in  the  usual
course of professional practice.”  Id., at 825. 

Both  Ruan  and  Kahn  filed  petitions  for  certiorari.    We 
granted the petitions and consolidated the cases to consider
what mens rea applies to §841’s authorization exception. 

II 
As we have said, §841 makes it unlawful, “[e]xcept as au-
thorized[,] . . . for any person knowingly or intentionally . . . 
to manufacture, distribute, or dispense . . . a controlled sub-
stance.”  We now hold that §841’s “knowingly or intention-
ally” mens rea applies to the “except as authorized” clause.