The CBI approached the apex court contending that the Nitish Kumar government was not legally empowered to move the high court against the order of acquittal of the Yadav couple by the state's designated CBI court as the crime had been probed by it.

Yadav and his former chief minister wife Rabri Devi were acquitted in December 2006 in a case in which they were charged with owning wealth exceeding their legal income.

Soon after the powerful Yadav couple, whose party Rashtriya Janata Dal is a key ally to the ruling United Progressive Alliance government at the centre, was acquitted by the trial court, the present state government had expressed its intention to challenge their acquittal in the state's high court.

The state government subsequently moved the Patna High Court, challenging the Yadavs' acquittal by the trial court, and the high court ruled Sept 20 this year that the state government was entitled to challenge the appeal.

It is against this order of the high court that the CBI has come to the apex court.

In its petition to the apex court, the CBI contended that only the central government was empowered to challenge the Yadavs' acquittal, owing to the fact that the case was probed by the central government agency.

"The Centre after considering the conclusions and findings of the trial court took a conscious and considered decision that no ground was made for filing of an appeal against the judgement of the trial court," the CBI said.

Incidentally, the railway minister and his wife too moved the Supreme Court last week, questioning the Nitish Kumar government's legal power, motive and rational to challenge their acquittal by the trial court.

In their petitions, the Yadavs had accused the Nitish Kumar of challenging their acquittal owing to political rivalry and vendetta.

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