The Estonian Threat

I just read an article in the NY Times about what Putin may do to stay in power. This paragraph struck me:

The other option would not require Mr. Putin to move out of the Kremlin even for a short time. According to the Russian Constitution, the president may declare martial law in the case of aggression or “direct threat of aggression.” A subsequent “martial law regime” could be easily fashioned by the Parliament to include the cancellation of elections until the “threat” is over. The “threat” could be found to emanate from Estonia, which has been sharply denounced by Russia’s official propaganda this year. Estonia’s ambassador in Moscow has been harassed by a government-organized youth group and its Web sites have been subject to cyberattacks.

I've got to wonder what kind of "threat" Eesti could pose to Russia to cause martial law? I can't even think of a made up threat that Russia could come up with that would require martial law, any ideas?