I disagree. I'm no lawyer but this didn't make sense to me so I reviewed the case...ok, I read a review of the case. I believe that drawing an inference from that case to this situation is not valid. The Kennedy case was one where an ex-spouse gave up her right to any pension benefits as part of a divorce settlement. But the participant did not change the beneficiary designation which named her as the primary beneficiary. Both she and the estate filed claims and the plan decided she was the beneficiary. I won't get into the legal reasoning but it went to the Supreme Court and they sided with the plan - she was the beneficiary because the beneficiary designation said she was, and a separate document waiving her rights had no impact.
The first sentence of the (Trucker Huss) review said: "In a victory for plan sponsors and administrators, the Supreme Court ruled recently in Kennedy v. Plan Administrator for DuPont Savings and Investment Plan, 129 S.Ct. 865 (2009), that retirement plans may rely on the plan terms and beneficiary designation forms in determining the proper recipient of survivor benefits." (My emphasis in bold.) Plan terms in the instant case say wife is beneficiary. No ifs and or buts; the designation signed by the participant before the marriage is simply invalid.