BAE has accepted the fine as fair
The High Court has granted an injunction to stop the Serious Fraud Office (SFO) striking further deals with UK defence contractor BAE Systems.
Last month, the firm agreed to admit two criminal charges and pay fines of £30m to settle UK investigations.
But campaigners asked for the injunction so they could apply for a judicial review of the settlement.
They are angry that claims of corruption will not be heard in court as a result of the deal.
The injunction is in force until the High Court decides whether to grant Campaign Against Arms Trade and The Corner House permission to apply for a full review of the settlement, which also involved £250m fines in the US.
It will make the decision by 20 March.
Campaigners have argued that BAE got off lightly, and that there should be a more thorough investigation into the allegations against the defence giant.
They say that the fines are simply administrative charges, and that corruption charges have yet to be investigated thoroughly.
The UK charge stems from a $39.5m (£26.4m) contract signed in 1999 to supply a radar system to Tanzania, and relates to payments to a former marketing adviser in the east African country.
The Campaign Against the Arms Trade has dismissed the £30m UK fine as a "tiny price" for BAE in the wake of an abortive investigation by the SFO into the company's contracts in Saudi Arabia.