If change is the only constant, how does the law keep pace with technology? Without a centralized judiciary, international law should be especially susceptible to disruption, yet it can be remarkably resilient in practice. I argue that efforts to minimize legal ambiguity, long seen as integral to compliance, can hinder its application to new technologies. Drawing on first principles from psycholinguistics, my theory differentiates between what I call convergent and divergent forms of flexibility. Unlike divergent flexibility, which gives rise to contestation, convergent flexibility tends to promote consensus, even when (1) technology is unprecedented and (2) regulatory interests sharply diverge. To test the theory, $450$ trained legal professionals were commissioned to take part in a randomized controlled trial (RCT) that varied technological novelty, legal precision, and political incentives. Participants collectively contributed 280,000 words over 10,000 hours in defense of their professional legal opinions, offering a novel (agent-subjective) measure of compliance. To establish external validity, the experiment is complemented with research into the legal impact of two breakthrough chemical weapons technologies: “super tear gas” and novichok. The findings contribute a general theoretical framework for understanding when and why emerging technologies are legally disruptive.

How does the threat of a dominant ally withdrawing affect public attitudes toward defense spending and defense cooperation in alliances? Despite extensive literature on foreign policy attitudes, we lack research that causally examines this pivotal question in a realistic setting. Addressing this gap, we utilize the novel circumstances surrounding the coin-toss 2024 US presidential election to test how the unprecedented uncertainty of the US commitment to NATO affects public attitudes toward defense in allied countries. Using a preregistered survey experiment in the United Kingdom, Sweden, and Germany, we investigate how an uncertain election defined by contrasting candidate rhetoric influenced European public opinion in an era of renewed Russian military threats. We find that US threats of withdrawal made respondents significantly more willing to spend on defense, and less willing to support continued defense cooperation in NATO. We demonstrate that threats of withdrawal also increased the public’s preference for national security autonomy, and explore whether declining confidence in NATO allies explains this effect. By inciting fears of abandonment, threats of withdrawal create concrete consequences not only for defense spending preferences, but also the types of cooperation that allies may pursue in lieu of the dominant ally’s commitment.