This is the question I asked repeatedly before our trip last month to Orient. I emailed the French prefet about where we'd quarantine if sick and never got a response. When I contacted the French side tourism office, they told me it would be handled by the Dutch side since the airport is there. I emailed the office handing the EHAS form on the Dutch side, and they said it would be handled by the French side since that's where we were staying. The person offered to find out about the policies on the French side, but I never heard anything back.