The Bangladesh high court has ruled that the corruption trial of former Prime Minister Sheikh Hasina is unlawful and cannot be held.
Sheikh Hasina says the charges are a ploy to keep her from office
It ruled that emergency laws could not apply to alleged crimes which took place years before the military-backed government seized power.
Correspondents say the ruling poses difficult questions for the government.
It hopes the order will be rescinded by the supreme court, which recently has overturned several high court rulings.
"It's a real victory. It has ensured the supremacy of the constitution," Sheikh Hasina's lawyer Rafiq-ul Huq said.
The attorney general's office immediately appealed against the ruling to the supreme court, which is due to hear the case on Thursday.
Correspondents say that if it is upheld, the government's efforts to tackle high-level corruption could be jeopardised.
Khaleda Zia also denies corruption
"The fate of all other graft cases under this regime will be determined by the verdict in this particular case," Ministry of Law adviser AF Hassan Ariff told the AP news agency.
Prosecuting lawyers on Wednesday decided there was no longer any point in proceeding with Sheikh Hasina's case until the supreme court ruling.
She and two family members deny receiving payments of about $435,000 from a businessman between 1996 and 2001.
They say that the allegation is politically motivated, and that the interim government's anti-corruption drive is simply an attempt to force the most popular politicians out of politics.
The prosecution say that Sheikh Hasina, her sister Sheikh Rehana and their cousin, Sheikh Fazlul Karim Selim - a cabinet minister during her administration - shared the money between them.
Emergency rule was introduced in Bangladesh after the caretaker government took power one year ago.
Instead of organising elections within three months as laid down by the constitution, the government said it first needed to clean up Bangladesh's corrupt political system.
Dozens of leading figures, including another former Prime Minister, Khaleda Zia have been held.
Lawyers argue that if the court orders the release of Sheikh Hasina, it would be hard for the government to prosecute other accused people.