The filed rate doctrine prohibits lawsuits which would challenge the appropriateness of any premium rate after it has been approved by a state insurance department. A few months ago I pointed to a December 2011 decision by a federal court in Kentucky throwing out an actuarial malpractice claim on those grounds.
That decision was follwed in January by a federal court in Kansas dismissing a class action complaint trying to challenge premium rate increases for long term care insurance as based on faulty actuarial assumptions. Armour v. Transamerica Life Ins. Co., No. 11- 2034 (D. Kan. Jan. 25, 2012).
So if you are an actuary working on rate filings, breathe a sigh of relief after the department of insurance approves the rate increase. Your work is not subject to attack in a subsequent suit by policyholders.