That's really strange. I work at a university and work with campaign organizers who bring candidates to our campus during presidential election years. Our local LE are paid by the campaign, not by the city or SS. We build the total cost of the rally on our campus (including campus LE, local LE and state LE) into what we charge the campaign to hold the event- both Republican and Democrat rallies/campaigns, and we work with city and state entities to do so. There may be LE who volunteer to work the event, but they are compensated for it through the politician's campaign through a signed contract ahead of time. The costs are spelled out and negotiated ahead of time with the campaign leads.
ETA: There is only one check or other form of payment provided from the campaign to the university, and we distribute the payments to others who also provided resources for the event, such as local and state LE, etc.