Issue Summary

It is possible to add a User Picker Custom Field or Group Picker Custom Field to Jira's Project Permissions, to have a specific set of users or groups granted permissions on an issue by issue basis.

The permissions are only granted upon saving these field values to an issue. This means that the permissions are not respected during Issue Creation, as the field value being set on the Create Issue form does not mean it has been saved yet.

Steps to Reproduce

We will use Assignee as our example, though this can apply to other permissions, such as Reporter

1. Create either a User Picker Custom Field or a Group Picker Custom Field, and associate it to all of a Project's screens
2. Grant the Assignable User project permission in the Project to either User Picker Custom Field or Group Picker Custom Field depending on which you'd like to test
3. During issue creation, set the custom field in question to the User or Group value that you'd like to add as an Assignee
4. Attempt to select an Assignee that only has permissions granted to it via the custom field

Expected Results

Users granted the Assignable User permission via the custom field are selectable as an Assignee

Actual Results

Users part of the User/Group Picker Custom Field cannot be selected as an Assignee

Workaround

Issues must be created without the intended Assignee/Reporter/etc., and the User/Group Picker Custom Field value must be set in it's own edit operation, before the permissions are reflected on those User/Groups. The Assignee/Reporter/etc. may then be set in a separate operation afterwards.