What laws cover the transit areas of international airports?
As of the writing of this question (6/25/13), Edward Snowden is presumed to be at SVO, but there is a disconnect between Vladimir Putin and Barack Obama about what that means. From the perspective of the United States, a wanted fugitive is in Russia, and in good faith Russia should return him. The Russian position, on the other hand, is that Snowden has not yet entered Russia, and therefore is protected.
My question is, what laws govern such spaces? Are transit areas normally subject to the laws of the country in which they are situated, or are they more akin to the extraterritoriality afforded to embassies on foreign soil?
Put another way, if a petty crime is committed in such an area, is that person subject to law in that country? If, say, a non-Muslim was caught proseltyzing in the transit area, or if an underage person was caught drinking, would the laws of the country apply, or would it be the laws of the country of which the person is a citizen?
Finally, if, as Russia claims, Snowden has not yet entered Russia, would the United States be legally justified in sending a police officer to Russia on a regularly scheduled flight, arrest him, and bring him home?