Usually, a parent who has custody of a child is entitled to change the residence of the child [California Fam.C. § 7501 (a)], but only if such parent has been awarded custody by way of a “final judicial custody determination” [F.T. v. L.J. (2011)].
Although there is a court order for “joint physical custody,” if one parent has only about 20% or less time spent with the child, that parent has only “nominal” physical custody, and in effect amounts to the “sole physical custody” of the parent with whom the child spends majority of the time [Marriage of Lasich].
To ensure that a move-away will be done properly and smoothly, and to avoid unnecessary distress, especially to the child involved, it is best to work with an attorney who is an expert in Family Law.