Several principles are quoted as the basis of
jurisdictional immunity:
a. Par in parem non habet imperium, i.e., an
equal has no authority over an equal.
b. The principle of non-intervention, i.e.,
the matters related to the acts, policy and
transactions of a foreign state should not
stand to scrutiny by the territorial state,
lest it would amount to intervention in the
internal matters of another state.
c. Rule of comity or reciprocity, i.e., the
accepted rules of mutual conduct as between
states, which each state adopts in relation
to other states and expects other states to
adopt in relation to itself. It may otherwise
be considered as an unfriendly act.
d. Implied grant of license to a foreign
sovereign or state to visit or function within
its territory signifies immunity and imposes
an implied obligation on the territorial state
not to derogate from such a grant.

"The customary international law rule that the
property of a foreign sovereign shall be immune
from attachment and execution, unless this
immunity has been waived by the foreign sovereign
expressly or impliedly." is a statement incorporated in Section 1609 of the 1976 Foreign Sovereign Immunities Act of the United States.