but probably the miscreant falsified the company forms only, making legal action unlikely to be appropriate.
On a point of order, in such circumstances legal action is not only wholly appropriate but the duty of any airline management with a proper sense of responsibility.
By "legal action" I mean, and I think you do too, reporting the crime to the proper authorities (Police and/or NAA) for investigation and prosecution, suspension of the pilot pending the hearing and summary dismissal if found guilty.
It makes no difference if he falsified a "company form". It's the falsification that is the crime, when done to secure a post as a pilot operating Public Transport aircraft. It is not just a civil matter between the pilot and the company.