Eligibility for inurnment at Arlington National Cemetery is verified at the time of need (time of death) and cannot be verified by the cemetery or accommodated before that time. Title 32 Code of Federal Regulations Part 553, Section 13, outlines which individuals are eligible for inurnment (columbarium or niche wall) at Arlington National Cemetery.
This federal regulation can be found here. Definitions of terms used can be found in Section 1 (553.1).
For an abbreviated list of eligibility rules, please refer to the attached fact sheet.