''The law of the country is the law'' Bava Batra [circa 35] does not mean in a case where it contradicts Torah. So women that get a divorce and then use that as a weapon to bankrupt their x's are violating Torah. Furthermore, they  transgress גונב נפש ומכרו מות יומת ["One who steals a soul and sells it shall be put to death."] when they use the court to take the children.  And the lashon hara [slander] that they engage in forever after has no conceivable permission. [However, there are times when speaking negatively is ok e.g., when one needs to warn someone not to be around a friend who is having an evil influence.]