Two anti-corruption groups have convinced a British court to delay final approval of a  controversial plea bargain between the U.K. Serious Fraud Office and arms company BAE Systems, complicating closure of what had already been a much-criticized prosecution.

The ruling, issued March 2, means that BAE cannot plead guilty to the charges it agreed with the SFO until the protesters have had a chance to make their case later this month that the plea deal should be struck out.

The SFO announced a settlement with BAE last month that is supposed to end its investigation into allegations that BAE used bribery and corruption to secure arms deals worth billions of dollars in several countries. The company agreed to a charge of poor recordkeeping and a fine of £30 million ($45 million). It also reached a linked settlement with the U.S. Department of Justice that will see it admit a charge of conspiring to make false statements to the U.S. government and pay a fine of $400 million.

Following the settlement, the SFO dropped its charges against the only individual it has sought to prosecute in the case, Austrian aristocrat Count Alfons Mensdorff-Pouilly, a BAE agent.

But protest groups Corner House and Campaign Against Arms Trade immediately protested the deal, claiming that BAE had got off lightly. They launched a joint application for judicial review, which would strike out the plea deal and force the SFO to reconsider a prosecution of both BAE and Mensdorff-Pouilly.

A judge has now issued an interim order to stop the SFO bringing the plea deal to court for approval until the application for Judicial Review can be heard. The judge ruled that a decision on whether to hear the review application would be made on March 20.

The two groups claim that, in agreeing to the plea and deciding not to prosecute, the SFO ignored its own guidance on plea discussions. They also claim that the decision was irrational, because the SFO could not “reasonably conclude” that the public interest factors tending against prosecution “clearly outweigh” those in favor.

They also argue that neither the British nor the U.S. settlements reflect “the severity of the alleged offending” and do not cover alleged offending in South Africa.