This article evaluates acceptance of the Tallinn Rules by states on the basis of eleven case studies involving cyberoperations, all occurring after the first Tallinn Manual was published in 2013. Our principal findings are that (1) it is unclear whether states are ready to accept the Tallinn Rules; (2) states show uneven interest in promoting legal certainty in cyberspace; and (3) a growing need for coordinated response to cyberattacks may induce states to consider more favorably the Tallinn Rules.