What doctrine applies when a party is prevented from asserting a claim due to another party's actions?

Equitable estoppel is the doctrine that applies when a party is prevented from asserting a claim because of the actions or representations of another party. This legal principle is rooted in fairness, aiming to protect parties from being misled or taking unfair advantage of another party’s reliance on certain representations or behaviors.

In essence, if one party makes a representation or takes an action that leads another party to rely on that representation or action, the first party may be "estopped" or barred from later claiming something contrary to that representation. For instance, if a landlord tells a tenant that they won't enforce a specific lease provision and the tenant relies on this to their detriment—perhaps by making renovations that would be against the lease's terms—the landlord may later be unable to enforce that provision against the tenant.

The other doctrines mentioned—res judicata, proximate cause, and strict liability—do not apply in this context. Res judicata addresses the finality of judgments and prevents a party from relitigating a matter that has already been judged; proximate cause pertains to the cause-and-effect relationship in tort cases; and strict liability involves holding a party liable for damages without proof of fault, typically in cases involving defective products. None of these concepts address the