French magistrates were to meet in a closed session on Monday to consider the party's appeal against an order to seize the funds.
RN leader Marine Le Pen has claimed the move would be a "death sentence" for the party, leaving it unable to pay employees and pursue other activities.
The party has launched an appeal for funds in the name of "political pluralism", raising 500,000 euros.
First use against political party
On 28 June Judges Claire Thépaut and Renaud Van Ruymbeke ordered the seizure of two million of the 4.5 million euros that the state should pay to the RN.
The procedure is sometimes employed against organised crime and alleged financial fraudsters but this is the first time it has been applied to a political party.
The judges argued that the state subsidy might be used to pay off existing debts, leaving nothing to reimburse the European parliament or pay fines if the case goes against it.
Parliamentary assistants' salaries
The National Front, as it was at the time, is accused of establishing a scheme by which its MEPs claimed expenses for parliamentary assistants but used the money to pay for full-time workers in France.
Among those charged are Marine Le Pen, her partner, Louis Aliot, and Nicolas Bay, who is expected to head the party's list in next year's parliamentary elections.
The RN says that the European parliament has already started proceedings to reclaim some of the money, but only against seven former MEPs.
Le Pen's lawyer, Rodolphe Bosselut, claims the public funding cannot be legally seized and that there is no risk of the party not honouring any possible repayments or fines.