The racial justice protests ignited by the murder of George Floyd in May 2020 constitute the largest protest movement in the United States. Estimates suggest that between fifteen and twenty-six million people protested across the country during the summer of 2020 alone. Not only were the number of protestors staggering, but so were the number of arrests. Within one week of when the video of George Floyd’s murder went viral, police arrested ten thousand people demanding justice on American streets, with police often arresting activists en masse. This Essay explores mass arrests and how they square with Fourth Amendment protections, as conceived by its Framers. The first part of this Essay provides an account of mass arrests during the George Floyd protests in Los Angeles, the city with the largest number of reported arrests in the initial demonstrations. The second part of this Essay begins by briefly reviewing the Expressive Fourth Amendment, a doctrine the author previously introduced, which posits that the Framers designed the Fourth Amendment to protect freedom of expression, in addition to the prevailing understanding of its safeguard of bodily integrity. The Expressive Fourth Amendment shields from government overreach individuals engaged in political expressive conduct. Here, this Essay expands upon this doctrine by querying how this protection should apply to mass arrests during protests and ultimately concludes that courts should demand both that a police officer establish probable cause for each protester swept up in a mass arrest and that judges positively weigh an individual’s expressive conduct when determining whether an arrest was reasonable in the totality of the circumstances.