* Says law allowing fresh rights trials unconstitutional
* Ruling effectively reestablishes controversial amnesty
By Malena Castaldi
MONTEVIDEO, Feb 22 (Reuters) - Uruguay's Supreme Court said on Friday that a law allowing fresh investigations of dictatorship-era human rights crimes violates the constitution, a ruling that puts dozens of cases into doubt.
About 200 Uruguayans were kidnapped and killed during the 1973-1985 dictatorship, and the small South American nation remains divided over how to deal with former military officers accused of rights abuses.
Congress passed legislation in 2011 that made new rights trials possible, in spite of a 1986 amnesty law shielding most officers from prosecution.
It contradicted the amnesty law by saying rights crimes cannot be subject to a statute of limitations.
Friday's Supreme Court ruling said two articles of the 2011 law were unconstitutional, a decision that effectively reestablishes the amnesty.
Despite the amnesty law, dozens of dictatorship officials were jailed for rights abuses committed during the dictatorship, including late former President Juan Maria Bordaberry and Gregorio Alvarez, who headed the military government from 1981 and 1985.
Moderate leftist President Jose Mujica spent more than a decade behind bars for his activities as a member of the Tupamaros guerrilla group in the 1960s and 1970s.
He has urged Uruguayans not to dwell on the brutality of military rule, but he backed scrapping the amnesty as part of his 2009 election platform. (Writing by Helen Popper; Editing by David Brunnstrom)