The St. Louis Post-Dispatch says "French Authorities" but it seems to be the European Food Safety Authority (EFSA). The study, however, was French.

It's "Roundup Ready" maize from Monsanto that's in question.

“The Authority's final review reaffirmed its initial assessment that the authors' conclusions cannot be regarded as scientifically sound because of inadequacies in the design, reporting and analysis of the study as outlines in the paper,” the authority said in a statement. “Consequently, it is not possible to draw valid conclusions about the occurrence of the tumours [sic] in the rats tested.”
I suppose this means they did get tumours, but we're not to worry about that.

Apparently, 700 scientists have signed a petition asking the author to disclose more information. But in his defence the Post-Dispatch reports:

... 200 scientists from 30 countries have supported the research.
and

Supporters have pointed out that the Seralini study, which lasted for the two years, was far longer and comprehensive that the industry's standard 90-day studies.
French authorities reject Monsanto-linked corn study : Stltoday