Hello,
Why not simply call him and remind him that you have reasons to draw his attention to the terms and conditions of employment, especially regarding the Notice Period. Don't get dragged into further discussion. This is a transparent yet tactful approach!
If after this, should the employee leave in defiance of the terms and conditions of employment and the Notice Period, you have the right (I suppose) in the contract of employment to not pay him the Notice Period, adjust balance PL, etc. You, in any case, withhold/indefinitely delay his clearance formalities and on that count hold F & F on all counts. This is the way the "administration" component of the HR job must act. Now it is for him to proceed against the company for recovering his dues.
Further, you can make the relieving letter, if at all you make it in this case, appropriately and give negative feedback to his potential employers, for what it will be worth.
Kindly do NOT be a captive of a mistaken notion that HR cannot/should not act tough or meet fire with fire! HR also has a backbone. If HR plays fair and receives an unfair response, then HR taking extreme steps is fully justified. Never forget that you are working for an ECONOMIC organization and NOT in a charitable organization (where you may, albeit wrongly, choose to be lenient at the costs of the funding agencies!)
Be fair, act rationally, don't ever initiate recourse to dishonest means and approaches!
Clear?
Good Luck.
Regards,
Samvedan
August 11, 2011