My employee has been charged with a DUI
I was not aware of his substance abuse.
He needs to drive for work.
As he was injured - I offered him to return to work on modified duties- not knowing of his DUI.
Can I terminate his employment.

This may amount to frustration of contract, if the employee's job is to drive and he is no longer able to do so, which may allow you to terminate his employment. We would need to review the details of his role, along with the employment agreement to be able to provide you with specific advice on this matter. Please contact us for a consultation.