Katie Holmes signed a confidentiality agreement as part of her divorce settlement with Tom Cruise.
The former couple - who split last month after five years of marriage - agreed conditions to end their union on Monday, with the terms said to include the actress agreeing not to speak about her estranged spouse's personal life or his religion, Scientology.
A source told the Daily Mirror newspaper: "Confidentiality was the key. If Katie hadn't signed up to remain silent it could have become a very messy legal battle."
Representatives with both stars have insisted the details of their settlement will be kept under wraps, though it is believed Katie will get primary custody of their six-year-old daughter Suri, with Tom allowed visitation rights.
The welfare of the little girl was key to the pair resolving their split amicably and privately following initial speculation there would be a public court battle.
However, sources told website TMZ.com that despite "palpable hostility" between Tom and Katie, a series of conversations concerning fears Suri could be "irreparably damaged" by their separation meant they agreed to come to a quick resolution.