Washington’s Department of Ecology (ECY) on Thursday published the final rule language that will enable its cap-and-invest programme to link with the combined California-Quebec carbon market, with the rules set to take effect on October 24. The move converts the linkage agreement signed by the three jurisdictions on June 25 into operational market plumbing, and it landed in the same week that California Carbon Allowance (CCA) futures slid to three-month lows around the $32 mark. For compliance buyers, traders and investors, North America’s second-largest carbon market is about to stop trading alone.
What the Final Rules Do
The ECY rule package updates Washington’s cap-and-invest programme so that its allowances can become fungible with those of California and Quebec, creating a unified market across the three jurisdictions. According to the Department of Ecology, the three governments signed their linkage agreement in June 2026, and California and Quebec continue to work through their own processes to complete the connection.
Washington’s programme, created by the 2021 Climate Commitment Act, is designed to cut the state’s greenhouse gas emissions 95 percent by 2050 compared with 1990 levels. Since its first auctions in 2023, it has operated as a standalone market with allowance prices that have historically traded well above California’s. Linkage changes that arithmetic: a combined market pools the allowance supply and demand of all three jurisdictions, and prices tend to converge toward the larger partner’s level.
The October 24 effective date matters for positioning. Compliance entities and financial participants now have a fixed regulatory horizon against which to plan allowance procurement, hedging and auction strategy for the fourth quarter.
The Market Is Already Pricing Convergence
The price signal arrived before the rules. CCA futures fell to three-month lows around $32 over the past week, according to Carbon Pulse’s WCI market report, pressured by September option expiry, an annual industry conference and, critically, the linkage plans with the Washington market. The July trading pattern showed CCAs already drifting toward $32 ahead of the third-quarter auction, so this week’s lows extend a softening trend rather than break a new one.
The logic is straightforward for traders. Washington allowances have carried a premium reflecting a smaller, tighter market. Once fungibility with California-Quebec supply becomes credible and dated, that premium compresses, and positions built on Washington scarcity get unwound. The three-month low in CCAs, rather than in Washington allowances, suggests the market is pricing the combined pool’s abundance, not just one jurisdiction’s balance.
For compliance buyers in California and Quebec, convergence at lower price levels reduces near-term compliance costs. For Washington-covered entities, it cuts the other way over time, as their allowance prices historically ran hotter and will now be anchored by the larger market.
CCUS Enters the Design Conversation
Alongside the linkage rules, Washington is widening the programme’s technology perimeter. A new ECY working group will examine integrating permanent carbon sequestration into cap-and-invest, the department’s cap-and-invest section manager said this week. That is an early-stage exploration, not a rule proposal, but it signals that carbon capture, utilisation and storage could eventually interact with allowance supply or offset eligibility in a linked WCI market.
The detail is worth tracking because linkage multiplies the effect of any design change. A CCUS integration decision made in Olympia would operate inside a three-jurisdiction market, and would likely pressure California and Quebec to clarify their own treatment of sequestration-based credits.
Implications for Buyers and Investors
For compliance buyers, the practical takeaway is a dated convergence trade with a regulatory anchor. Entities covered in any of the three jurisdictions should revisit fourth-quarter procurement and hedging plans against the October 24 effective date, and model compliance costs at converged price levels rather than jurisdiction-specific ones.
For investors and traders, the linkage sequence offers a defined catalyst calendar: rule effectiveness in late October, then the remaining legislative and regulatory steps in California and Quebec. Each milestone either validates or delays the convergence pricing now visible in CCA futures.
For project developers selling offsets into WCI, a linked market enlarges the addressable buyer base but also intensifies scrutiny of offset supply. California’s offset usage limits and Washington’s own offset provisions will now interact within one pool, so developers should map eligibility rules across all three programmes rather than optimising for one.
What to Watch
Three markers will determine whether linkage proceeds on schedule. First, whether California and Quebec complete their own linkage processes before year-end, since Washington’s rules alone cannot create a shared market. Second, the first joint auction results after linkage takes effect, which will show where the combined price settles relative to the $32 level. Third, the output of the ECY working group on carbon sequestration, an early signal of how the linked market might treat permanent removals in its next design phase.
