There is, I think, a difference between property owned by foreign private individuals. Embassys, on the other hand, are a different matter. Those are considered foreign soil and those countries can exercise their laws over it.
Look at a similar matter, that of the naval base at Guantanamo Bay. We hold that through a treaty signed with the government of Cuba over a hundred years ago. When Castro seized power he unilaterally voided the treaty and demanded the U.S. leave. The U.S. has refused for over 40 years and has continued to pay the required nominal rent into an government account in Europe. If the Davis regime was within its rights to demand Fort Sumter and to shell it when the Lincoln Administration refused to leave then wouldn't the Castro regime be within its rights to shell Guantanamo Bay?