Document ID: ./input/supremecourt_opinions/opinions/22pdf/21-1496_d18f.pdf
Page Number: 5.0

Cite as:  598 U. S. ____ (2023) 

5 

Syllabus 

presented as agnostic as to the nature of the content.  At bottom, the 
allegations here rest less on affirmative misconduct and more on pas-
sive nonfeasance.  To impose aiding-and-abetting liability for passive
nonfeasance, plaintiffs must make a strong showing of assistance and 
scienter.  Plaintiffs fail to do so. 

First, the relationship between defendants and the Reina attack is 
highly attenuated.  Plaintiffs make no allegations that defendants’ re-
lationship  with  ISIS  was  significantly  different  from  their  arm’s 
length, passive, and largely indifferent relationship with most users.
And their relationship with the Reina attack is even further removed,
given the lack of allegations connecting the Reina attack with ISIS’ use
of these platforms.  Second, plaintiffs provide no reason to think that 
defendants were consciously trying to help or otherwise participate in
the  Reina  attack,  and  they  point  to  no  actions  that  would  normally 
support an aiding-and-abetting claim. 

Plaintiffs’ complaint rests heavily on defendants’ failure to act; yet
plaintiffs identify no duty that would require defendants or other com-
munication-providing services to terminate customers after discover-
ing that the customers were using the service for illicit ends.  Even if 
such  a  duty  existed  in  this  case,  it  would  not  transform  defendants’ 
distant  inaction  into  knowing  and  substantial  assistance  that  could 
establish  aiding  and  abetting  the  Reina  attack.    And  the  expansive 
scope of plaintiffs’ claims would necessarily hold defendants liable as 
having aided and abetted each and every ISIS terrorist act committed
anywhere in the world.  The allegations plaintiffs make here are not 
the type of pervasive, systemic, and culpable assistance to a series of 
terrorist activities that could be described as aiding and abetting each
terrorist act by ISIS. 

In  this  case,  the  failure  to  allege  that  the  platforms  here  do  more 
than transmit information by billions of people—most of whom use the
platforms for interactions that once took place via mail, on the phone, 
or  in  public  areas—is  insufficient  to  state  a  claim  that  defendants 
knowingly gave substantial assistance and thereby aided and abetted 
ISIS’  acts.    A  contrary  conclusion  would  effectively  hold  any  sort  of 
communications provider liable for any sort of wrongdoing merely for 
knowing that the wrongdoers were using its services and failing to stop
them.  That would run roughshod over the typical limits on tort liabil-
ity and unmoor aiding and abetting from culpability.  Pp. 21–27.

(2) The  Ninth  Circuit’s  analysis  obscured  the  essence  of  aiding-
and-abetting liability.  First, the Ninth Circuit framed the issue of sub-
stantial assistance as turning on defendants’ assistance to ISIS’ activ-
ities in general, rather than with respect to the Reina attack.  Next, 
the Ninth Circuit misapplied the “knowing” half of “knowing and sub-
stantial assistance,” which is designed to capture the defendants’ state