By signing the treaty, EU member Latvia officially recognized the post-Soviet borders with Russia, backtracking on its earlier territorial claims on the Pytalovsky District, which was part of the Baltic state before World War II.
The treaty, signed March 28, was submitted to parliament April 10.
Latvia's Constitutional Court previously refused to suspend the ratification procedure following a suit by a faction in Latvia's parliament.
New Times said earlier that the treaty violated the Latvian Constitution, since the Latvian government had unlawfully changed the state border.
Deputies said the government should have asked the Latvian people if they supported the decision to give up the country's claims to the Pytalovsky District, in the Pskov Region, in exchange for an improvement in political and economic ties with Moscow.
