JIRA doesnt respect the ASSIGNABLE permission while moving issue

Summary

JIRA doesn't respect the ASSIGNABLE permission while moving issue.

Environment

• JIRA 6.4.10
• JIRA 6.3.15

Steps to Reproduce

1. Disable Allow unassigned issues
2. Create two projects: project A and project B
3. Set the default assignee to Project lead in project B
4. Emptied the ASSIGNABLE permission in project B
5. Create issue in project A
6. Move issue to project B

Expected Results

Issue move should fail with "The default assignee does NOT have ASSIGNABLE permission OR Unassigned issues are turned off."

Actual Results

The issues is moved and still assigned to the current assignee

Workaround

Ensure the default assignee has the ASSIGNABLE permission