Contrary to what perhaps popular culture might have us believe, the law that is applicable in an embassy is the law that is applicable in the "receiving state". An embassy does not constitute foreign soil, and remains subject to the sovereign law of the state in which it is located.
A United States embassy, however, remains the territory of the receiving state, and does not constitute territory of the United States. Restatement (Second) § 77 comment a. Thus, United States embassies are not within the territorial jurisdiction of the United States.
McKeel v. Islamic Republic of Iran, 722 F. 2d 582 - Court of Appeals, 9th Circuit 1983