Unless he has a contract or union agreement guarantying him a position (i.e. that you'd hold it) for a certain length of time or otherwise preventing you from terminating him in this situation, you don't have to hold his position at all: if there is no contract, he is an employee at will, and an employee at will may be terminated at any time, for any reason, including for being arrested. (The law does not require employers to keep employees who are arrested.) There is no obligation in the law to put him on leave at all, for any time--you can immediately terminate him.If there is a contract covering this situation, then you need to review the terms of the contract to see what you can do, when.