This person really should not be working for the airline for a few reasons.
Firstly, they have an addiction and apparently have not made any effort to cure it. (i am probably going to be crucified for drawing this analogy, but anyway) Just as an alcoholic or heroin addict suffers an illness (addiction) so does this person. And for the same reasons that the heroin addict or alcoholic would be dismissed if they refused treatment, this person should also be dismissed. Not only because of the physical manifestations of cravings etc but because of the psychological effects of an adicts performance.
Is their mind really on the job at hand when they are thinking about the next hit, or in this case, the next steal. For this reason alone this person should have been counselled and dismissed.
However, there is another reason and it's related to AN employment policy.
AN like Q, has anti-theft policies in place that make removing AN property from the aircraft a dismissable offence. AN cannot hope to rely on these policies if it allows this person to repeatedly steal and remain employed. I know he did not steal from AN on this occasion, however, it shows a pattern of conduct upon which AN is entitled to rely.
The same goes for any pilot caught DUI in their own car on their day off. It shows a willingness to disregard others safety and AN would be justified in at the very least suspending an employee convicted of such an offence.