This might be more of an immigration law issue. My understanding of the F1 visa is that you are granted entry to US to study in a college, university, etc. An F1 student may work in US so long as it is tied into his/her area of study. So for example an F1 law student can work at the law library, book store, admissions office, etc. at least on a part time basis. I dont see any problem with an F1 student doing volunteer work but I need to know more facts as to what you are referring to. You should consult with an immigration attorney as well. Good luck. Nick Ebrahimian.