Oxford University has applied to the High Court for an injunction against animal rights protesters who campaign against its biomedical research centre.
The university wants to limit protests at the site
It says that since building of the £20m centre resumed last November, threats and criminal damage have risen.
QC Charles Flint said the injunction was needed to protect staff and students, adding an activist had made "clear threats" against the university.
The university wants to extend the exclusion zone around the site.
Mr Flint said Robin Webb of the Animal Liberation Front (ALF) told the media that student accommodation was a legitimate target.
He was also caught on camera showing an undercover journalist how to make a bomb, the QC said.
"There can be no dispute whatsoever that the ALF is a criminal and terrorist organisation and there are persons unknown who have taken action in the name of the ALF against the university," he said.
Mr Webb's counsel, Stephanie Harrison, applied for an adjournment of the case so he could answer properly.
Oxford University already has temporary injunctions that limit when and how protests can take place, and also protect a wide group of university-related people from harassment.
It allows a demonstration opposite the site on South Parks Road, on Thursday afternoons, but bans protest activities within the exclusion zone.
It says builders have faced threats and disruption and there has been criminal damage at the site since work resumed there in November.
Earlier this month, a steel contractor decided to withdraw from the building project because of concern he would become a target.
Police evidence also revealed instances of people following vehicles from the site.
Mr Flint said on the evidence there was "an overwhelming picture of real distress, alarm and harassment".
Oxford wants to limit weekly demonstrations to a maximum of 12 people - down from 50 - for an hour at lunchtime.
It also wants to extend the injunction to provide the same level of protection for those who supply goods and services.
Professor Colin Blakemore, chief executive of the Medical Research Council, told BBC News the university and Oxford itself was "living under constant threat".
He said demonstrations by relatively large groups of people were very disruptive to the work of the university and to students' studies.
He said: "What the university is seeking to stop here is the growth of a mood of violent and aggressive protest against the university and everyone associated with the university.
"Agreed, nobody is comfortable with the idea of restrictions of freedom of expression of opinion; it's not really aimed at that.
"It's not attempting to stop all demonstration. It's just looking for a reasonable balance and relief for the university and the city from the constant, constant harassment."
But Mel Broughton, of animal rights group Speak, told BBC News the restrictions could lead activists to more extreme forms of protest.
He said: "It goes way beyond what's necessary.
"What they're seeking is in fact an attack on the right to protest; it has nothing to do with curbing criminal activity.
"I'm afraid that this continued attack on the legal process is likely to have the effect where some people would give up on the whole idea of legal process and take to a process outside the law."
Last month, Mr Justice Holland said it would be irresponsible to grant the university the injunction it wanted.
The latest hearing, in London, is expected to last three days.