California is one of those headache states whose officials unfortunately don't seem interested in working with anybody who has packgoats. Ask them to send you a link to "LMP Standard S-9" so you can look at it in writing. Ask them to also send you a copy of the San Bernardino forest plan and do a search for the keyword "goat".
The plan I found in a very quick search was this one:
https://www.fs.usda.gov/Internet/FSE_DOC...007719.pdf
The only place it refers to goats is on page 100 under the pack and saddle stock regulations. It says, "Goats are not permitted in wilderness with bighorn sheep herds."
And that's it. This is very vague language which does not, in my opinion, constitute a forest-wide ban. It looks like it only applies to designated wilderness areas that contain bighorn sheep. You'd have to do some research to find out what is designated wilderness vs. FS/BLM, and which wilderness areas contain bighorns. I know that some forest plans in California were trying to ban goats preemptively before bighorn sheep were even introduced, but in this case it specifically states that goat are only prohibited from areas where bighorn sheep already live.
As far as disease risk to bighorns, this is a summary of what we know:
https://www.napga.org/resources/
It's worthwhile to take some time to sit down and read some of those documents since they contain a lot of very good information. One that I encourage people to print out and show to wildlife officers is the
NAPgA Summary of Understanding at the bottom of the page.
I looked up your name in the NAPgA membership database and I see you are a member. This means you can access other members' contact info through the website. (Go under the "Membership" tab and do a Member Search by state for "CA" or look at the Member Map.) I encourage you to call or email some goat packers who live in California and get their take on it or see if they can put you in touch with FS officers who are reasonable to talk to.