ByteDance Ltd.’s Hail Mary legal effort to avoid selling or shutting down TikTok relies on convincing a judge the social network will disappear entirely, squashing the free speech rights of millions of Americans.

The drawback to that argument is that the merest whiff of a deal to offload the app to new owners would fatally undermine the case. No free speech is lost if TikTok merely changes hands, a judge might say.