WI AB400

Creates a civil cause of action allowing minors (or their parents/guardians) to sue health care providers who perform gender transition procedures on individuals under 18 if the minor suffers physical, psychological, emotional, or physiological injury from the procedure or its aftereffects

Permits recovery of declaratory/injunctive relief, compensatory damages, punitive damages, and attorney fees for prevailing parties, with a statute of limitations extending until the individual reaches age 33

Defines "gender transition procedure" to include puberty blockers, cross-sex hormones, and gender reassignment surgeries, but excludes treatment for medically verifiable disorders of sexual development or emergency medical situations

Establishes a "safe harbor" defense for providers who document 2 years of consistent gender incongruence, obtain written certification from at least 2 health care providers (including a mental health professional) that the procedure is the only treatment option, and confirm the minor has no other mental health concerns

Requires providers claiming the safe harbor defense to deliver a mandatory written and oral notice at least 30 days before treatment (and at subsequent visits for 6 months) warning of risks including potential for regret, lack of FDA approval for puberty blockers, infertility, and costs potentially exceeding $100,000