broadly speaking it's illegal to volunteer for duties that are part of/the same as your paid work, and NPS interprets this to apply to seasonals who are between seasons (& presumably also those who've had offers rescinded). i know the laws don't matter anymore, but still

joy is important and it makes resistance sustainable. joy is - can be - a good byproduct of meaningful politics! but joy is not in itself resistance; emotions are not political and they are not action.

this article doesn't say anything specific about probationary employees

running parks with volunteer labor sets a terrible precedent. rangers are professionals, often with many years of experience and a lot of education, and volunteers cannot run parks nearly as well as the paid staff.