Is it possible to reassign issue based Resolution field selection?

[Bar T]

Not sure how to Post Function this.

We want all resolution = defer to be assigned to a certain person. Is this possible to set in Jira Server?

[Tuncay Senturk]

Have a look at this post function 

Assign to a user in a role, based on a field of issue post function

[Meg Holbrook]

Hey Barbara, give this addon a try: Automation for JIRA

What you're asking for can be accomplished with the suite of automation tools provided, and it's relatively inexpensive (will depend on your user base though).

[Steven F Behnke]

This would typically be accomplished by developing an Event Listener that inspected issues as they were modified and if it encounters a Deferred issue, to modify the assignee field.

[Bar T]

Is an event listener an add on feature? Thanks Steven.

[Nic Brough -Adaptavist-]

Yes, you will need some code to implement a listener to do this.  There are several automation add-ons that could help you do it - Automation for Jira and ScriptRunner for example.