A Chicago Judge recently sided with a divorced man who did not want his 9 year-old son to undergo a circumcision procedure. Circuit Judge Jordan Kaplan said that it was an "extraordinary medical procedure" for a 9 year-old and the boy can decide for himself when he reaches age 18.
The father sued to block the operation in a dispute with his ex-wife. The couple's 2003 divorce decree stated that he had to be consulted before the child underwent any "extraordinary" non-emergency procedure which is language typical of legal custody.
This case is an example of the power that a legal custodian can wield even if s/he doesn't have physical custody. Make sure that your divorce or paternity decree clearly spells out each party's legal (and physical) custodial rights. Typically there is case law or statutory language that can be incorporated to ensure that both parties have a clear understanding of what rights they are entitled to and what is expected of them.