The Doctrine of State Immunity means a State cannot be sued in the courts of another State without its consent.

The key distinction is the nature of the act: immunity applies to sovereign/governmental acts (jure imperii), but not to commercial or proprietary acts (jure gestionis). Philippine courts apply this doctrine as part of international comity and respect for sovereign equality.

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Holy See v. Rosario, Jr., G.R. No. 101949, December 1, 1994 (Supreme Court; Lawphil).

A civil suit was filed against the Holy See over a lease of property used as a diplomatic residence. The Supreme Court dismissed the case, holding that the Holy See is a sovereign entity with international juridical personality and enjoys state immunity, because the lease was sovereign in character (jure imperii), not a commercial transaction.

🥜 A sovereign State (or entity) is immune from suit for sovereign acts; immunity is lost only when the act is commercial (jure gestionis).

🚨 Bar Trap:
Do not confuse state (sovereign) immunity with diplomatic immunity—the former protects the State/entity, the latter protects individual diplomats.