Russia's prosecutor-general is reviewing the legality of a decision in 1991 granting three Baltic countries independence from the Soviet Union, a spokesman said on June 30.
The move follows the office's ruling last year that Crimea was illegally handed to Ukraine in 1954 and is setting off alarms in the small ex-Soviet states of Lithuania, Latvia, and Estonia.
It drew a furious reaction from Lithuania's President Dalia Grybauskaite.
"No one has the right to threaten" us, she said. "Our independence was gained through the blood and sacrifice of the Lithuanian people."
Two lawmakers from the majority United Russia party argued in their appeal to prosecutors that decisions by the State Council of the Soviet Union, which granted independence to Estonia, Latvia and Lithuania, were illegal.
The lawmakers claimed that the decisions "brought great harm" to the country and should therefore be qualified as "state treason," according to the appeal, which is now under review.
The Prosecutor-General's Office is "reviewing the request by lawmakers in accordance with Russian law," a spokesman said.
Lithuania was the first of three countries to declare independence in 1990, followed by Estonia and Latvia in rapid succession. The State Council, which was chaired by former Soviet President Mikhail Gorbachev, recognized their independence in 1991 in its inaugural session.
Lithuanian leaders reacted angrily to the review.
"I hope this meaningless action will be stopped," Foreign Minister Linas Linkevicius said, calling the move a "provocation."
The initiative may not gain much traction in Russia, where some top officials seemed skeptical about it.
"I haven't heard anything about the query," Russian Foreign Minister Sergei Lavrov told reporters in Vienna. "What I do know is that we have diplomatic relations and interstate treaties with these Baltic countries."
Interfax quoted an anonymous source at the Prosecutor-General's Office as saying that even if he found the Baltics' independence to be illegal because the State Council was not authorized to grant it under the constitution, there would be no real legal consequences today because Russia has no way in practice to change the decision.
The matter would become a "political matter" that would have to take into account today's realities, the Interfax source said, including the Baltic nations' membership in NATO and the Pentagon's recent decision to base hundreds of battle tanks, high-caliber weapons, and as many as 5,000 troops in the region.
Still, the lawmakers' request raises chilling questions, especially in light of Russia's move to annex Crimea and back pro-Russian separatists in eastern Ukraine.
Clearly, lawmakers in Moscow are growing more assertive about challenging the world order created after the fall of the Berlin Wall. Russia has seen a number of bills calling historical facts into question.
Last year, a group of lawmakers asked prosecutors to look into decisions taken by Gorbachev that led to the dissolution of the Soviet Union.
With reporting by AFP, Interfax, and TASS