Short answer: Seven jurisdictions ban tobacco rating entirely: California, the District of Columbia, Massachusetts, New Jersey, New York, Rhode Island, and Vermont (Connecticut bans it only on its state Marketplace). Elsewhere insurers may add up to a 1.5x surcharge.
Federal ACA rules let insurers charge tobacco users up to 50% more (a 1.5:1 ratio), but states can be more restrictive. In those jurisdictions, smokers and non-smokers pay the same rate. Where the surcharge is allowed, the plan must offer a tobacco-cessation program, and completing it removes the surcharge. Tobacco is one of only four factors the ACA permits for pricing, along with age, geography, and family size.
Sources
CMS, Market Rating Reformscms.gov/marketplace/private-health-insurance/market-rating-reformsKFF, tobacco surcharges in the Marketplace and state limitskff.org/faqs/faqs-health-insurance-marketplace-and-the-aca/marketplace-health-plans-and-premiums/can-i-be-charged-higher-premiums-in-the-marketplace-if-i-smoke