Bustamante-Barrera v. Gonzales, 447 F.3d 388 (5th Cir. Apr. 20, 2006) (sole - not joint - "legal custody" by a naturalized parent is required for a child seeking derivative naturalization; requirement not met where divorce decree awarded "sole physical custody" of child to mother, but required parents to share "joint legal custody.").
http://caselaw.lp.findlaw.com/data2/circs/5th/0560247cv0p.pdf