You're probably thinking of one of two pieces of litigation against UA. The first was one by million mile flyers that had their lifetime benefits reduced and tier retitled and a new 75K tier inserted between their 50K tier and 1K. The other one was litigation by the Silver Wings flyers, a program offering discounts to senior flyers that paid a membership fee, that also promised benefits that seemed to have disappeared. I recall one of the judges in the million miler case questioning a UA exec who pretty much did respond that they could do whatever they wanted with their program, even with past promises.

Lifetime Silverwings members file class action against UA

Million Miler Sues United [Judgment for UA Jan 2014] Judgment Affirmed Dec 2014