kennedy became the most senior associate justice on the court following the death of antonin scalia in february 2016. since the retirement of sandra day o'connor in 2006, he has been the swing vote on many of the court's 5–4 decisions. he has authored the majority ruling in many of these cases, including "lawrence v. texas", "boumediene v. bush", "citizens united v. fec", and "obergefell v. hodges".