Montrose Chemical Corp. of Cal. v. Superior Court

Summary

The court held that, in a continuous-injury case, an insured may access an excess policy after exhausting directly underlying excess insurance purchased for the same policy period, rather than first exhausting all lower-level excess insurance across every triggered period. The court reasoned that the policy language, the historical function of other-insurance clauses, and the insured's reasonable expectations favor vertical exhaustion, while insurers may seek contribution or reimbursement from other liable insurers. The judgment was reversed and remanded for further proceedings, including consideration of an unresolved choice-of-law issue concerning certain policies.