Most protesters were arrested before getting near the site
Civil rights campaigners have won the right to challenge police use of anti-terror powers against protesters at an arms fair.
A demonstrator, backed by the campaign group Liberty, has won a full hearing at the High Court in London after applying for permission to seek a judicial review of the police action.
Student Kevin Gillan, 26, from Sheffield, was stopped by police outside the exhibition in London's Docklands by police using section 44 of the Terrorism Act 2000.
Mr Gillan said he was felt humiliated on being searched when his only
intention was to exercise his right to protest peacefully.
A Liberty spokesman said: "The essence of our case is that anti-terrorist legislation should not be
used to curb legitimate protest."
Mr Justice Maurice Kay said the hearing to take place after 1 October would decide whether or not the demonstrator had a case.
Police have now arrested a total of 144 people since 1 September, in moves against protests at the Defence Systems and Equipment International (DSEi) exhibition.
Three people attached themselves to a delegates' coach leaving the Thistle Hotel at Tower Bridge on Friday morning, said police.
Human rights contravened
Most of the arrests were under public order legislation, for offences such as blocking the highway and criminal damage.
But police said at least two arrests this week had been under the 2000 Terrorism Act.
Liberty has complained that "dozens" of others were stopped and searched in an inappropriate use of section 44 of the Act, contravening human rights legislation.
John McGuinness, appearing for Sir John Stevens, had said David Blunkett should be the sole defendant as he had sanctioned the use of the anti-terrorism laws.
But the home secretary has sought an explanation from police as to why they used the act.
He said police use of the law had been authorised in the run-up to the second anniversary of 11 September.
But it was intended for use against "terrorist attacks or measures that we had to take to counter terrorists," he said.
He told MPs on Thursday the Act would be discredited if it was wrongly used by police.
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"Initial findings overnight indicated that two non-British nationals were
picked up and the police believed that they were justified in doing so under the Terrorism Act.
"I need to know that other people on whom the Act was applied were
justified," he said.
Police who used the same powers against
demonstrators at RAF Fairford in July, but Mr Blunkett said they had acted properly because some protesters
had been armed with "cudgels and swords".
London Mayor Ken Livingstone has also said he would be seeking an explanation from Scotland Yard.
Metropolitan Police Deputy Assistant Commissioner Andy Trotter said the law had been used "appropriately" in "exceptional circumstances".