Compelled Hosting Isn't Rendered Unconstitutional by Mistaken Public Assumptions of Endorsement
Another excerpt from the First Amendment section of my Social Media as Common Carriers? article (see also this thread); recall that the key First Amendment arguments are in this post, which relies on the PruneYard, Turner, and Rumsfeld precedents, and in this one, which explains why Miami Herald, Hurley, and the various other "common theme" precedents don't apply.
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Of course, whenever visitor V speaks on host H's property, there is always some possibility that some observers will assume that H at least views V's speech as acceptable (even if H didn't choose the speech and doesn't expressly endorse it). After all, property owners are usually allowed to decide what behavior, including speech, is allowed on their property, and a decision not to expel a speaker may be seen as in some measure approving of the speaker.
But say the law requires H—such as a shopping mall owner, a cable system, a university, a phone company, or a shipper such as FedEx or UPS—to let certain speakers use its property. Once people know this is the law, they can no longer reasonably assume any such endorsement. And H can generally explain to the public that it's hosting such speakers as a matter of legal command, not of voluntary decision.
Such an ability by property owners to "expressly disavow any connection with the message" (a message that is itself clearly written by others), and to point out that the message is only allowed "by virtue of [the] law," suffices to prevent any First Amendment violation. Observers can be expected to "appreciate the difference between speech [the property owner] sponsors and speech the school permits because legally required to do so, pursuant to an equal access policy," especially when nothing "restricts what the [property owner] may say about" the third party's speech. And the same is true for platforms, which can easily inform readers that they aren't endorsing particular writers, or more generally that they aren't endorsing speech on their sites as a whole.
Of course, there's always the risk that some people wouldn't understand that a social media platform that hosts, say, a Nazi or Communist page is merely following the law—or that they would understand, but would still be upset at the platform, or even threaten to boycott it. But the same risk was present in Rumsfeld; indeed, it was greater in Rumsfeld, because the Solomon Amendment merely threatened universities with loss of federal funds if they exclude military recruiters, so universities weren't exactly "legally required" to include them. "[S]tudents will in fact perceive their schools as endorsing the military's discriminatory policies" if they hosted military recruiters, reasoned the amicus of brief of various law student associations, "particularly if schools provide the type of affirmative assistance demanded under the Solomon Amendment." Yet the Court viewed this possible inaccurate perception as irrelevant.
This risk of mistaken perception of endorsement was likewise present in PruneYard. Yet the property owner's opportunity to "expressly disavow any connection with the message" was seen as sufficient to preclude any First Amendment challenge to the common-carrier-like requirement. The same should apply to social media platforms. A passage from Board of Ed. of Westside Community Schools v. Mergens, which Rumsfeld expressly quoted in rejecting the risk of misperception, is particularly apt here:
[P]etitioners' fear of a mistaken inference of endorsement is largely self-imposed, because the school itself has control over any impressions it gives its students. To the extent a school makes clear that its recognition of respondents' proposed club is not an endorsement of the views of the club's participants, students will reasonably understand that the school's official recognition of the club evinces neutrality toward, rather than endorsement of, religious speech.
The school's control over students' perceptions is of course imperfect, but it is substantial enough to make the "mistaken inference of endorsement" irrelevant. And the same is true for social media networks, which likewise have many tools to influence readers' perceptions, and to "make clear" that their hosting various views "is not an endorsement of the views." As the Court later put it, there can be no "modified heckler's veto," in which speech could be barred based on what some "members of the audience might misperceive."
To be sure, a social media platform might not want to have to disclaim any connection with offensive speech by its users, and might prefer just to block such speech so as to avoid giving such a disclaimer. Yet Rumsfeld and PruneYard show that such a preference does not make the mandated hosting unconstitutional. The lower court decision in Rumsfeld, for instance, struck down the law in part because it pressured universities into responding to the recruiters:
[S]peech with which the law schools disagree [has] resulted in, according to the record, hundreds (if not thousands) of instances of responsive speech by members of the law school communities (administrators, faculty, and students), including various broadcast e-mails by law school administrators to their communities, posters in protest of military recruiter visits, and open fora held to "ameliorate" the effects of forced on-campus speech by military recruiters. All of these represent instances in which the schools were "force[d] … to respond to a hostile message when they would prefer to remain silent."
But the Court was unmoved by this concern, and instead noted the university's ability to respond (whether or not it would have "prefer[red] to remain silent") as a basis for upholding the hosting requirement. (While the plurality in Pacific Gas & Electric Co. v. Public Utilities Comm'n seemed to take the view that such pressure to respond made a hosting compulsion unconstitutional, that plurality has not carried the day, and in any event seemed to limit its analysis to exclude cases where, as in PruneYard, the government "simply award[s] access to the public at large." And Rumsfeld seemed to have limited the Pacific Gas plurality to situations where the speech that someone is compelled to host "tak[es] up space"—presumably referring to scarce space—that the host would otherwise use "to communicate its own message.")
 447 U.S. at 87. The Court suggested that "[t]he views expressed by members of the public in passing out pamphlets or seeking signatures for a petition thus will not likely be identified with those of the owner," because the mall is generally "open to the public to come and go as they please." Id. But even for those observers who make the "not likely" assumption that the speech is endorsed by the mall, "appellants can expressly disavow any connection with the message by simply posting signs in the area where the speakers or handbillers stand. Such signs, for example, could disclaim any sponsorship of the message and could explain that the persons are communicating their own messages by virtue of state law." Id.
Compare Hurley, where the Court held that disclaimers would be insufficient, because "Although each parade unit generally identifies itself, each is understood to contribute something to a common theme, and accordingly there is no customary practice whereby private sponsors disavow 'any identity of viewpoint' between themselves and the selected participants. Practice follows practicability here, for such disclaimers would be quite curious in a moving parade." Hurley v. Irish-Am. Gay, Lesbian & Bisexual Grp. of Boston, 515 U.S. 557, 576–77 (1995). For reasons discussed in Part II.F. 1 below, that analysis doesn't apply to social media posts. And Hurley of course expressly declined to "decid[e] on the precise significance of the likelihood of misattribution," because it found it "clear that in the context of an expressive parade, … the parade's overall message is distilled from the individual presentations along the way, and each unit's expression is perceived by spectators as part of the whole." Id. at 577.
 Rumsfeld, 547 U.S. at 65 (emphasis added); see also Turner Broad. Sys., 512 U.S. at 655–56 (noting that "there appears little risk that cable viewers would assume that the broadcast stations carried on a cable system convey ideas or messages endorsed by the cable operator," especially since "it is a common practice for broadcasters to disclaim any identity of viewpoint between the management and the speakers who use the broadcast facility").
 Nor would the platforms need to put up such disclaimers every time an item from the platform is seen (for instance, every time a Tweet is embedded in some post). If a law does require the platforms to host various materials, all it would take is for the platforms to sufficiently inform the public about that law—something the Facebooks and Twitters of the world have ample communicative resources to do, for instance using a clickthrough warning that they can show once or a few times to their users.
 Brief Amici Curiae of the National Lesbian and Gay Law Association, Law Student Associations, et al., Rumsfeld v. FAIR, 2005 WL 2347167, *7.
 496 U.S. 226 (1990).
 547 U.S. at 65 (quoting Mergens, 496 U.S. at 250 (plurality opin.) and a similar passage in id. at 268 (Marshall, J., concurring in the judgment)). Mergens upheld a statute that required public schools to allow religious or ideological clubs on the same terms as other clubs. Marshall's separate opinion expressed the concern that students might not get the message if all they see are religious clubs: "If a school has a variety of ideological clubs, … I agree with the plurality that a student is likely to understand that 'a school does not endorse or support student speech that it merely permits on a nondiscriminatory basis.' When a school has a religion club but no other political or ideological organizations, however, that relatively fine distinction may be lost." Id. at 268. But of course a massive social media platform notoriously contains "a variety of ideological" messages.
 Id. at 251. The argument begins on p. 250 of Mergens ("we note that Congress specifically rejected the argument that high school students are likely to confuse an equal access policy with state sponsorship of religion") and continues onto p. 251.
 Good News Club v. Milford Central School, 533 U.S. 98, 119 (2001). As with Mergens, Good News Club involved the question when student groups' religious speech could or should be restricted in public schools, based on a concern that other students will misperceive the speech as being endorsed by the school. But this Establishment Clause question is closely analogous to the Free Speech Clause of when compelled access rules violate the compelled speech doctrine, based on a concern that other visitors will misperceive the speech as being endorsed by the property owner—as the Court recognized in relying on Mergens in Rumsfeld.
 FAIR v. Rumsfeld, 390 F.3d 219, 239 (3d Cir. 2004), rev'd, 547 U.S. 47 (2006).
 547 U.S. at 65.
 475 U.S. at 1, 15–16 (1986).
 For more on PG&E and its tension with the other cases I discuss here, see Volokh, The Law of Compelled Speech, supra note 114, at 383–86. "The result in Pacific Gas may have been justifiable on the grounds that the law offered access only to certain speakers, or offered access that was in part triggered by Pacific Gas's speech, or otherwise interfered with Pacific Gas's speech (for instance, by decreasing the amount of space that Pacific Gas could use for its own messages). But the 'pressure to respond' argument does not seem adequate as an independent basis to strike down speech restrictions, and indeed PruneYard, Turner, and FAIR appear inconsistent with it." Id. at 386.
 475 U.S. at 12.
 547 U.S. at 64 (internal quotation marks omitted).