From the Matter Spec:
> 2.3. Network Topology
> [...]
> This protocol may operate in the absence of globally routable IPv6 infrastructure. This requirement enables operation in a network disconnected or firewalled from the global Internet.
> 2.3. Network Topology
> [...]
> This protocol may operate in the absence of globally routable IPv6 infrastructure. This requirement enables operation in a network disconnected or firewalled from the global Internet.
May implies it is up to the manufacture is internet (i.e globally routable IPv6 infrastructure) if required or not.
Confusingly, in legal terms "may" can also indicate a mandatory provision, depending on the context. https://www.law.cornell.edu/wex/may