Every program modifies values saved in your computer's RAM. It adds values, modifies them, and erases them. It's the core function of any program.
Criminal offense can only be charged if a program tampers with private user's data (passwords, usernames, intercepting packets from online servers or modiying packets before they are sent to servers or even spoofing these packets for private information).
You, as a game company, can take him to court, but its doubtful that any hacker will be criminally charged just by making a simple single-player trainer.