Technically speaking, anything not Phase 3 is legally considered "R&D material" and needs remediation to be compatible with California law, however obtaining Phase 3 is almost impossible for the average cannabis enthusiast, unless dealing directly with a licensed dispensary, distributor, or manufacturer.

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To achieve a clean end product, each process must follow strict non-contamination guidelines.  For nurseries to produce Phase 3-compliant plants, they must either employ a sterile environment or an organic integrated pest management system, or both.