Start immediate deportation of Russian nationals.

Military intervention on the territory of a foreign state under the pretense of protecting Russian nationals is totally unacceptable.
Moscow says it is defending the interests of its nationals in Ukraine, but if we were to accept that argument - then Russian forces could invade any other country at any other time for the same reason.
If the presence of Russian nationals in any country presents such a threat, we (and every Western Democracy) should prevent Russians from entering our country and start immediate deportation of Russian nationals.