Key to the concept of Omerta is that any member of the organization must maintain absolute silence when questioned by law enforcement on the subject of alleged illegal activities by other members of the organization. This can result in one member "taking the fall" for others, facing criminal contempt of court charges or even taking sole responsibility for a crime that others committed. He does this with the assurance that he and his family will be supported by the organization during and after his imprisonment.
They were able to make charges stick on one of them, but he wouldn't talk -- omerta. He did six months, and now he works at Tony's restaurant.
"Whoever appeals to the law against his fellow man is either a fool, or a coward. Whoever can not take care of himself without that law is both. For a wounded man shall say to his assailant, "If i live, i will kill you, if i die, you are forgiven", such is the rule, of Omerta"