According to documents provided to the daily by a judges' union, the plan would extend the period police can keep a suspect in detention without charge or a hearing before a judge to up to six months.
Suspects would also not be able to contact a lawyer until after spending 24 hours in custody.
Under the plan children could be tried in adult courts and more trials held behind closed doors.
The Syndicat de la Magistrature called the measures "revolting" and said they would amount to "liberticide," and called on Justice Minister Michele Alliot-Marie to abandon the plan.
The union was due to release on Tuesday the text of the government plan, which it said was provided to heads of courts in great secrecy in July, the newspaper reported.
Swine flu, or the A(H1N1) virus, the first pandemic to be declared by the World Health Organization in this century, has so far claimed 15 lives in France, out of at least 2,837 worldwide.
The French government has conducted extensive planning to prepare for an expected new wave of infections as the autumn flu season approaches in the northern hemisphere.