Does your appointment letter mention that 'the consumption of alcohol and other substance abuse, during the work hour is punishable amounting to termination '?
In case you don't have it so far, please include it as early as possible. Reporting to work under the influence should be included in this clause.
Please perform medical checks to bring it under control. We used to arrange sudden medical checks at the workplace. It doesn't take too much, but helps in bringing a control over the discipline at the company.
Each time anyone is reported to work under the effects of alcohol, please take stern actions. A consistent program to eradicate this habit will show a result in the long run. You may face initial dissent, but stay at it. You will be creating a substance abuse free workplace.
I am attaching few warning letters as contributed earlier. You need to include the Alcohol and substance abuse clause in it. Please consult with your reporting managers on the actions to be taken and create three escalating level punishment, for non-adherence.
Furthermore, please consult your company lawyer on this. It should not create a safety hazard and defect in your workplace standards. Warning letters doc
(Cite Contribution) 9th April 2011 From India, Mumbai