Filing case against an employee (false allegations that company is forcing to sell Ganja and other drug items)

Recently we removed a employee from the service as he was creating lot of problem in day to day work. He was also not signed NDA. But he created a union and creating more and more problem. After termination, he is still sending email to Government (Project awarded from Govt for the year of five years period) and misguiding. Due to this, its very difficult us to concentrate our upcoming other projects.
Today he also attached an email and sent to Govt saying that the company is forcing us to sell Ganja and other drug items. Its totally and utterly false allegations.
He is sending such type of messages to government and misguiding and try to terminate the company. Can we file a criminal case against his such unpleasant emails or can we file civil case against him. Please advice sir.

Send him a legal notice asking him to stop forthwith such false accusations and ask him withdraw and submit an open public apology failing which legal action can be taken against him
Before all this, i do hope your company has terminated him by following due process for termination.
Courts can be approached only when your hands are clean.
One employee(ex) making allegations and company is getting disturbed.There is no reason together disturbed if you have done right actions.
Take calm actions-legal notice, clarification to the concerned govt agency about irresponsible allegations against company.