Currently going through this. I have primary custody and received a job offer in Seattle (we're in California). My ex is fighting the relocation. Under California Family Code § 7501, the custodial parent has a presumptive right to relocate, but the non-custodial parent can object and the court will evaluate the best interests of the child. My attorney says the key factors are: (1) the reason for the move (career advancement is viewed favorably), (2) the impact on the child's relationship with the other parent, (3) the child's ties to the current community, and (4) whether a modified custody arrangement can preserve the non-custodial parent's relationship.