Don't panic, be prepared to overwhelm the IO with "proof" as to your authorization for on-campus employment. Start with what is directly available of USCIS's website:
1. Print out and highlight the section on the
Handbook for Employers M-274 where it clearly states:
"F-1 students may work on campus
without approval from USCIS until they complete their course of study." - When you print out this page, be sure it shows the USCIS name and logo for authentication.
2. Print out and highlight the section on
SEVIS/Employment from ICE where it states:
"
An F-1 student automatically has permission to work on campus (unless he or she is a border commuter) but still needs to work with a DSO to ensure the job offered qualifies as on-campus employment.
An F-1 student will need certification letters from the DSO and the employer. The student must present these letters to officials at the local Social Security Administration office to
get a Social Security number."
**You will need to get certification letters from your DSO if you do not already have that to include with the REF response**
**Take you time to review the above link to ICE, you'll see other sections you may be able to reference.
3. Print out and highlight the section
8 CFR 214.2(f)(6)(H) where it clearly states:
"On-campus employment pursuant to the terms of a scholarship, fellowship, or assistantship is deemed to be part of the academic program of a student otherwise taking a full course of study"
and
8 CFR 214.2(9)(i)