Power production was halted in December 1996 for maintenance. However, following a court case led by opponents of the reactor, on February 28, 1997 the Conseil d'État (Supreme State Administrative Court) ruled that a 1994 decree, authorizing the restart of Superphénix, was invalid. In June 1997, one of the first actions of Lionel Jospin on becoming Prime Minister was to announce the closure of the plant "because of its excessive costs". As Jospin's government included Green ministers, pro-nuclear critics argued that Jospin's decision was motivated by political motives.