Dear Ms. Cardines,
Thank you for posting your request on History Hub!
According to this finding aid for the series Draft Registration Cards, 1917-1918 in the Records of the Selective Service System (World War I) (Record Group 163), “citizen Indian” is one of the potential categories of citizenship that would make one eligible or ineligible for the draft. You may contact the National Archives at Atlanta (RE-AT) at firstname.lastname@example.org for access to and information about these records.
The term “citizen Indian” can also be found in other records, including the series The Indian School Journal, 1904-1926 in the Records of the Bureau of Indian Affairs (Record Group 75), which includes 3 references to "citizen Indians". These records have been digitized and can be viewed online in the Catalog. Please contact the National Archives at Fort Worth (RM-FW) at email@example.com with any questions you may have about these records. The series Numerical Index to the Central Classified, 1907-1942 in Record Group 75 also includes 4 references to "citizen Indian". These records have been digitized and can be viewed in the Catalog, and you may contact the National Archives at Washington, D.C. - Textual Reference (RDT1) at firstname.lastname@example.org with questions about these records.
Due to the COVID-19 pandemic and pursuant to guidance received from the Office of Management and Budget (OMB), NARA has adjusted its normal operations to balance the need of completing its mission-critical work while also adhering to the recommended social distancing for the safety of NARA staff. As a result of this re-prioritization of activities, you may experience a delay in receiving an initial acknowledgement as well as a substantive response to your reference request from RE-AT, RM-FW, or RDT1. We apologize for this inconvenience and appreciate your understanding and patience.
The US Army Center of Military History also offers this bibliography related to American Indian Military Service that may be of interest to you. The dissertation “American Indians in World War I: Military Service as Catalyst for Reform” by Thomas A Britten, for example, is included in the bibliography, and it discusses draft registration and enlistment issues related to citizen Indians vs. non-citizen Indians. A PDF of the dissertation is available online if you search for it by the title and author.
We hope this information is helpful, and best of luck with your research!