Well, it depends on if there has been an order prior to a finalization of divorce or if you simply leave the marriage by moving out of state. See the custodial interference statute under kidnapping.  It appears this crime is committed if you have no legal right to take the child.  So, if your spouse somehow gets an order against you (like a temporary or permanent restraining order) to keep you from the child, then you may be committing this offense.

45-5-304. Custodial interference. (1) A person commits the offense of custodial interference if, knowing that the person has no legal right to do so, the person takes, entices, or withholds from lawful custody any child, incompetent person, or other person entrusted by authority of law to the custody of another person or institution.
     (2) A person convicted of the offense of custodial interference shall be imprisoned in the state prison for any term not to exceed 10 years or be fined an amount not to exceed $50,000, or both.
     (3) With respect to the first alleged commission of the offense only, a person who has not left the state does not commit an offense under this section if the person voluntarily returns the child, incompetent person, or other person to lawful custody before arraignment. With respect to the first alleged commission of the offense only, a person who has left the state does not commit an offense under this section if the person voluntarily returns the child, incompetent person, or other person to lawful custody before arrest.