If PoS makes ETH a security, how exactly does the SEC plan to regulate it? Will they establish official policy that validators and full-nodes would be expected to follow, internationally or only nodes operated in the US?

The SEC's potential regulation of ETH as a security under PoS is a complex issue. If deemed a security, the SEC might establish guidelines for validators and full-nodes, but enforcing these internationally could be challenging. They may focus on US-based nodes and exchanges, potentially creating a fragmented market.