Is a court bound by interlocutory order requiring a father to pay his ex-wife's attorney fees and costs in a custody dispute?

In Lucachevitch v. Lucachevitch (1945) 69 Cal.App.2d 478, 159 P.2d 688 the parents of a young boy agreed to joint custody of the child. The father [217 Cal.App.3d 1283] later sought exclusive custody of his son; the mother filed a countermotion, also seeking sole custody. The trial court modified the custody decree and awarded the mother attorney's fees and costs. The father appealed, contending that pursuant to the parties' interlocutory decree he was no longer responsible for his former wife's attorney's fees.