It is important to strike a balance between responsibility and empathy in situations like this, in the one hand, if the behaviour of an employee with a gambling addiction is affecting work performance or the work environment, of course strict measures such as dismissal may be necessary to maintain professionalism, stability and productivity at work, but, on the other hand, it is also very important that the company provides support and assistance to the employee struggling with addiction, but that it if he really wants to quit gambling and not to cover up his mistakes.
unfortunately a company could very well much argue that as long as he is not their employee it is none of their business how he is doing mentally which is why it would just be easier to let go an employee having a hard time dealing with things such as addiction
it also doesn’t help that there is a stigma against gamblers, addict or not, they can always claim that he isn’t an addict and he just really likes gambling which is his conscious choice to keep doing