Ok, thirty miles from St. Petersburg and in your opinion that portion of Russia and any portion of Russia that borders one of the Baltic States should be some sort of DMZ where Russians aren't permitted to put their own troops on their own soil, gotcha.
Sorry, I don't see it. Russia has every right to move troops wherever it likes within its own nation and that includes near the Baltics whenever the Baltic States are beating the war drum and holding NATO maneuvers on those borders.