The San Juan County COVID-19 page is silent on this, but there appears to be a health order from the San Juan County Public Health Officer that some county officials have recently publicized to reduce transient travel into the islands. Found some actual reference material for the group to judge and act accordingly.
mynorthwest.com has a short news item about it at
https://mynorthwest.com/1815668/san-juan-county-council-bans-visitors/? The mynorthwest.com article is misleading or incorrect, in stating the order is from the County Council because I cannot find anything on the SJC website or their COVID site about the council doing any such thing.
But the mynorthwest.com article contains a link to this page
https://www.visitsanjuans.com/travel-advisory which is a REQUEST from the San Juan Islands Visitors Bureau not to travel, including not going to marinas or to shore if you anchor. It does however, mention that the San Juan Islands Historical Park is open with limited facilities available. So technically, the boater headed to Garrison Bay and wanting to land and walk his dog could land at the park, at least according to their website...
HOWEVER, the Visitors Bureau page states their request is based on the order of the San Juan County Health Officer...
The Deer Harbor Marina website is actually a much better source of real information. They are not taking transient moorage based on the Health order, and provided the order they are complying with. Here is the link to the actual San Juan County health order
https://www.sanjuanco.com/DocumentCenter/View/20042/San-Juan-County-Health-Officer-Order-2020-1?bidId=
The order does indeed ban travel for non-essential reasons, and says it is prohibited and punishable by law. Their Sheriff and Prosecutor are taking an educate and inform posture, but aren't ruling out civil court processes for "more serious offenders." You can read their release of information here.
https://www.sanjuanco.com/DocumentCenter/View/20179/200410-Sheriff-PA-Community-Update
As for the Coast Guard doing the inform/educate bit? If I was them I would want to make sure travelers stayed away too since there is a health order - they don't want to get the call of the sick COVID boater than needs evacuation either...
Good luck to all, and please stay healthy!