The Patna High Court on Friday admitted two petitions challenging the formation of a new government by Nitish Kumar's JD-U along with the BJP.
The development comes as the assembly met for a special session for the floor test of the new government.
The court has, however, not fixed a date for hearing the two petitions that were filed on Thursday, a lawyer of the RJD said.
One petition was filed by Jitender Kumar and the second by Rashtriya Janata Dal legislators Saroj Yadav and Chandan Kumar Verma.
They contended that the mandate in the 2015 Bihar assembly polls was given to the Grand Alliance of the JD-U, RJD and Congress led by Nitish Kumar against the BJP and that it was to rule for five years.
They have also said that the Rashtriya Janata Dal is the largest party in the state assembly but Governor Keshari Nath Tripathi did not invite it to form the new government after Nitish Kumar resigned on Wednesday after he dumped the Grand Alliance.
The petitions said that as this was against the Constitution, the court should intervene and dismiss the newly formed Nitish Kumar government formed with the BJP's support.