The expression wrongful expression is not a technical description known to the law, but those who use it are presumably referring to either an unfair dismissal or a dismissal brought about in contravention of a contractual right which the employee has. A remedy for unfair dismissal has been created by
legislation (the Fair Work Act federally and the Industrial Relations Act in Western Australia). It is not a cause of action recognized by the common law, which is the law of the land not made by legislation, but created over centuries by the courts. Breach of contract, for example, is a common law remedy whereas the seeking of a remedy for a termination of employment brought about unfairly is a right of action created by the Parliaments.