From what I've read most states are doing the following, which is in line with what the NPS is doing. I've seen several of our parks with historical items such as lodges, trams, forts, visitor centers are closed for preservation of those places while no one is manning them. Some parks are being manned by staff who live on site, but will not have direct contact with the public. Some will answer phones and aid in emergency situations. Essentially, parks that have visiting hours only are closed. Where I am, Texas:
Buy all permits online ahead of time. Self pay stations will have very limited availability.
No new backcountry camping permits, but if you have one already, you can still use it.
No staffing of any kind except if the park has police/security and/or fire/rescue. NPS parks are free to enter. No trash, guided tours, ranger services, etc. Texas is pay station only access, but there is no one from TPS monitoring campsites.
No group camping or picnicking allowed. (10 or more).
No gatherings of any kind of more than 10 people anywhere.
Guidelines that should be obvious now.
Bring some kind of comms due to very limited police/fire presence at most parks. A mobile phone may not be enough.
Pack out way more than you pack in. People are stupid and figure "someone else will pick up this trash if I lay it next to the overflowing trash can".
Social distancing (which is the whole point of camping)?
Consider self portable toilets as vaults and port-a-johns will fill and are not being maintained.
Boondocking shouldn't be an issue at all, anywhere... and more importantly, there really isn't anyone policing the parks so be safe, be smart and keep an eye on your potential neighbors.
