The way on where people could be caught up on doing gambling activities is on the time that they've been already get hired and then doing all of those things which there's someone could
make out some report but knowing previous or things in life before getting the job is impossible.Everything could really be denied if they wanted to.
I believe you, there no way an applicant will disclose this kind of information knowing that he will not be getting the position once the hiring officers know his gambling background, they will surely denied things and the only way that it can be revealed is when problem start to show up, but if there's nothing that will affect the employee's job role there's nothing that the company should held them responsibility.
It's their life, and it's outside the business, unless, again, if there's any effect with the job and the company.
Employers can quickly terminate the employee, it's part of their right when proven that there's a problem with the person involve.