What happens if an assignee of a part interest refuses to join in an application for reissue?

If an assignee of a part interest refuses to join in an application for reissue, the reissue may still be applied for by the assignee of the entire interest. This is outlined in MPEP 1410. The assignee of the entire interest can file the reissue application as the sole applicant. However, the assignee must comply with the requirements of 37 CFR 1.172, which includes submitting an oath or declaration by the assignee.