Is it permissible for a father who works in the Public Funds Prosecution to restore the rights of those who have been swindled, including those who work in usurious banks? Does this conform to Sharia? What is the punishment for fraud and swindling in Sharia, knowing that the court may not apply the Hudud (prescribed punishments) of Sharia?

Fraud and deception are forbidden in Islamic law. Their punishment is discretionary (ta'zir), determined by the judge in a manner he deems appropriate to discipline the perpetrator, along with obliging him to guarantee or return what he took. Discretionary punishment may include imprisonment and banishment. Your father's work in this field is permissible, and he must perform his work with justice and restore rights to their owners, even if they are usurers or disbelievers, as Allah Almighty says: "O you who have believed, be persistently P.O.Q.S. for Allah, witnesses in justice, and let not the hatred of a people prevent you from being just. Be just; that is nearer to righteousness. And fear Allah; indeed, Allah is Acquainted with what you do."