How can we prevent the assignment of case to the user who is not currently logged in salesforce?

Hi Mohit,

You can prevent the assignment of case to the user who is not currently logged in salesforce by Creating a formula field in the case that assign value of Current user id .
Then in the case assignment rule use the formula
($User.Id== formula field in case )

Create rule for each user with same formula.

Hope this helps you.

Thanks