Can I place a no trespassing sign/ private property on my cabin?

The Forest Service frowns upon posting any No Trespassing signs anywhere in the National Forests. Any sign you want to place on your cabin needs to be authorized by the local district officer in your Forest.

I have seen one or two signs in or on cabins, but those seem to be overlooked exceptions. Check with your forest and if you have particular concerns, also share those with the agency officers. Increased crime is a concern that sometimes needs to be communicated.

One option I've seen that appears to comply with Forest Service policy and also serves to give notice to non-permit holders is a sign that say's, "Private Residence". These signs are readily available at hardware stores and online. Here's an example on Amazon:

https://www.amazon.com/dp/B01COXVWJS/ref=twister_B01NA0O1HC?_encoding=UTF8&psc=1

Dave

We've not looked into for our cabins, but we did ask about our docks a few years back and, at that time, FS said something along the lines of "Dock Use Restricted - FS Special Use Permit Holders Only" was okay.

To add to the dialog above, the Forest Service frowns upon any signage which attempts to restrict general public access to National Forest lands, including our lots.  Since the cabin is your private property, you can post a sign identifying your cabin as "private property" and you may also be allowed to say something like "no public access allowed" or "keep off" or "no trespassing" if the sign is clear that it applies to your private improvements, but not the lot.