Understanding the 2025 California Prop 65 THC Warning Rules for Hemp

California's Proposition 65 (Prop 65), officially known as the Safe Drinking Water and Toxic Enforcement Act of 1986, has been a staple in regulatory compliance for all businesses selling consumer products in California. The law compels businesses to provide clear warnings if their products expose consumers to chemicals known to the state to cause cancer, birth defects, or reproductive harm. In 2025, the Office of Environmental Health Hazard Assessment (OEHHA) ushered in significant amendments—directly impacting hemp and cannabis operators, especially those selling products with delta-9 THC.

This analysis provides an up-to-date review of what the new Prop 65 amendments mean for the hemp industry, especially around short-form warnings, online and catalog sales, enforcement, and how these updates relate to other packaging, labeling, and consumer safety rules.

What Changed Under the 2025 Prop 65 Amendments?

The amendments to Prop 65 came into effect on January 1, 2025, with immediate changes for businesses. However, OEHHA has provided a generous three-year transition period (through end of 2027), allowing businesses time to adjust their labeling and e-commerce practices to meet the latest requirements (source).

Key highlights:

• THC, including delta-9 THC, is now explicitly regulated under Prop 65 for developmental toxicity. This means products containing delta-9 THC, even hemp-derived, may require a Prop 65 warning if exposures meet or exceed the significant risk level.
• Short-form warnings have been tightened:
  • Warnings must now name at least one listed chemical (e.g., “delta-9 THC”).
  • The short-form warning option is now explicitly available for food products but comes with restrictions on font size and label area.
• Internet and catalog sales face clarified requirements:
  • Warnings must be provided both before purchase (on the product display or description page) and during checkout.
  • The warning content must be as clear as what is provided on-product.
  • Digital warnings must ensure consumers cannot bypass them before completing a purchase.
• Enforcement actions remain active, including 60-day notices against brands failing to provide compliant warnings for delta-9 THC exposures from hemp products.

The Latest Short-Form Warning Rules: What Hemp Brands Must Know

When Can Short-Form Still Be Used?

Under the 2025 rules, short-form warnings are more limited but still practical for many packaged hemp products. The revised regulations demand:

• At least one listed chemical by name (such as “delta-9 THC”)—general warnings like “this product contains chemicals…” are no longer sufficient.
• Minimum font size of 6 points.
• Label area less than 5 square inches or where space constraints make the long-form impractical.

Example Short-Form Warning for Hemp Products Containing Delta-9 THC

WARNING: Exposes you to delta-9 THC, which can cause developmental harm. See www.P65Warnings.ca.gov/cannabis

For multiple endpoints (e.g., cancer and reproductive toxicity), additional language and listed chemicals may be required. Check the official OEHHA guidance for the safe harbor warning template most suitable for your category.

Key Restrictions & Format Obligations

• Do not rely on old generic short-form warnings after January 1, 2028.
• If your product label is larger than 5 inches or has ample space, the full (long-form) warning may be required.

Internet and Catalog Sales: New Duties for Online Hemp Retailers

Prop 65 has always required warnings to reach consumers before purchase, but the 2025 amendments clarify exactly how to deliver these via e-commerce channels:

Where Internet Warnings Must Appear

• Product display page (or a prominent link such as “⚠️ WARNING” adjacent to the price or product name).
• Checkout/cart page before the sale is finalized—consumers should have to see (and cannot easily bypass) the warning.

These dual requirements ensure the warning isn’t missed due to design quirks or inadvertent clicks. For catalog sales, the printed material must contain the warning near the product description.

How Detailed Must Online Warnings Be?

Warnings presented online must match the substance and prominence of the physical label. So, if your product uses the short-form with chemical name (“delta-9 THC”), the same specificity is required in your digital warnings.

For full details, review the updated safe harbor methods at OEHHA’s official Prop 65 site (Direct Link).

Transition Timeline for Hemp Operators

• Effective Date: January 1, 2025. Compliance is expected immediately for all new products.
• Transition Period: Existing products have until January 1, 2028 to update short-form warnings, packaging, and internet protocols. After that, enforcement against old warnings is likely to strengthen (see analysis).

Enforcement Trends and Compliance Risk: Recent Lessons

Since THC (including hemp-derived delta-9) is now a listed reproductive toxicant for Prop 65 purposes in California, the past year has seen a steady stream of 60-day notices targeting brands for noncompliant packaging, especially where e-commerce and retail shelf warnings were missing or outdated.

• Penalties: Violators may face lawsuits, civil penalties, and mandatory corrective action.
• ‘Private enforcer’ actions (where individuals or advocacy groups file suit) remain the most common means of enforcement.
• Warning requirements are strict liability—good faith errors are not a defense, so robust compliance systems are vital.

Latest notices and settlements indicate particular scrutiny of:

• Edible and inhalable hemp products with delta-9 THC
• Products marketed via national e-commerce platforms
• Packaging and online interfaces not updated for the 2025 warning details

Data and current notices can be tracked via the California Attorney General’s 60-Day Notice Portal.

Prop 65, Child Safety, and Packaging: Navigating Overlapping Laws

Prop 65 warning requirements now operate alongside several other key cannabis and hemp safety rules under California and federal law:

• Child-resistant packaging: Required for all high-THC cannabis and often for hemp-derived products under DCC and federal rules.
• Child-appeal/marketing restrictions: Products that resemble candy or are marketed with child-like graphics face extra scrutiny.
• Age-gating: California prohibits the sale of hemp or cannabis products containing THC to minors. Online sales must use robust age-verification systems—ensure that Prop 65 warnings do not conflict with age gating, and that minors are not exposed to the warnings or offered product access.
• Labeling harmonization: Warning text must be clear even as packaging displays other cautionary logos or seals. Never ‘hide’ a Prop 65 warning behind child-proof seals or under opaque flap designs.

OEHHA has not provided a Prop 65 exemption for compliant child-resistant packaging or for products sold strictly to adults. Businesses must comply with all sets of rules (Prop 65, DCC, FDA, etc.).

Clear Takeaways for California Hemp Businesses in 2025

1. Audit your product warnings now. Do your current hemp product labels and online sales touchpoints name delta-9 THC, in the format and prominence now required?
2. Upgrade your e-commerce site to ensure warnings are visible before and during checkout, and match label content/presentation.
3. Map your packaging and product timelines to update stock for full compliance well ahead of the January 1, 2028 transition deadline.
4. Monitor enforcement actions and stay alert for new 60-day notices affecting hemp, CBD, and THC products.
5. Coordinate Prop 65 efforts with age-gating, child-resistant packaging, and DCC labeling compliance—gaps or inconsistencies can invite regulatory scrutiny or litigation.
6. Stay engaged with OEHHA and compliance professionals for periodic updates as regulations, chemical listings, or warning templates may change.

California’s evolving Prop 65 regime is a core area of compliance for every hemp and cannabis brand looking to sell in the Golden State. Understanding how these warning requirements intersect with other safety laws is not optional—it's essential for business continuity and risk mitigation.

For up-to-the-minute guidance and to simplify your compliance journey, rely on CannabisRegulations.ai—your trusted source for regulatory updates, packaging protocol checklists, and expert insights into California's complex cannabis and hemp market.