Implicitly marking the 20th anniversary of its seminal decision in Knight v. Jewett, which established the doctrine of primary assumption of the risk, the California Supreme Court confirmed both the continuing vitality and breadth of that decision in Nalwa v. Cedar Fair (2012), S195031. In Knight, a plurality of the Supreme Court held that a player in a touch football game had no duty to prevent injuries resulting from the inherent risk of playing this contact sport. In Nalwa, the Court confirmed 6-1 that this doctrine remains the law in California and also that it extends to the operator of bumper cars at an amusement park, and the inherent risks of, well, bumping. In both cases, the Court held that the only duty of operators, sponsors and fellow participants engaged in a recreational activity with inherent risks was not to increase those risks.

Guided by the facts in Knight, and its companion case Ford (which applied this doctrine to noncompetitive waterskiing), the most common application of primary assumption of the risk has involved physical sports, although the courts have sometimes used a broad definition of "sport," including: downhill skiing (Cheong – colliding skiers), baseball (Avila – injury from an inside pitch), motorcycle “off-roading” (Distefano – colliding motorcycles), golf (Shin – getting hit by an errant ball), sport fishing (Mosca – getting hit with a someone else’s fishing line ), rock climbing (Regents – falling to death after anchors gave way), river rafting (Ferrari – rider struck her head on the raft frame), and even a noncompetitive group bicycle ride (Moser – colliding bicycles), and a group motorcycle ride toy drive (Amezcua – against the organizers, after a 3rd party collided with a motorcycle). This doctrine also extends to the training and instruction of athletic activities, so that coaches and trainers have a duty not to increase the inherent risks of training for and learning a given sport (e.g., Kahn – addressing a coach’s instructions to dive into a shallow pool). Sports spectators also assume the risk of being in the vicinity (e.g., Nemarnik – hockey fan hit by a puck).

However, the language in Knight and Ford is broader than just sports or athletics, and more generally addresses recreational activities, repeatedly referring to the inherent risk in "the activity or sport" at issue. Following suit, a recent lower court decision abandoned any pretense that an activity had to be considered a sport and applied primary assumption of the risk to an injury resulting from participation in the closing fire ritual at the annual Burning Man festival, an event which was not, in any way, a sport. In Beninati, the plaintiff tripped and fell into the remains of a substantial bon fire, having deliberately walked through the remaining embers. In essence, the court found that if you play with fire you may well get burned, and no one else has a duty to prevent this.

In Nalwa, the Supreme Court clarified the scope of primary assumption of the risk as it applies to recreational activities, consistent with Knight and Ford, whether or not the activity might constitute a sport, such as bumper cars. As clarified, the doctrine applies to 1) recreational activities, 2) that involve an inherent risk of injury, 3) to voluntary participants, 4) where the risk cannot be eliminated without altering the fundamental nature of the activity, 5) and in which the participants are actively engaged. The last point was the basis on which Nalwa distinguished bumper cars from roller coasters. Once engaged, bumper cars are individually controlled by each driver, much like players in a sport, and this is an inherent part of the activity. In contrast, participants are only passively engaged in roller coasters, having surrendered all control over the carriage to the operator, who is therefore held to the duty of a common carrier for hire (as held in Gomez). Finally, this doctrine is not barred by the existence of regulations governing the recreational activity, including safety regulations, although such regulations could establish negligence per se, or set the bar on what risks are considered inherent.