British authorities detained David Miranda, the partner of Guardian reporter Glenn Greenwald, for nine hours on Sunday under a counterterrorism law. They held Miranda, 28, a citizen of Brazil, incommunicado and interrogated him without giving him the opportunity to secure legal counsel.

Miranda was stopped by British officers as he passed through London’s Heathrow Airport on his way from Berlin to his Rio de Janeiro home, which he shares with Greenwald. The officials released Miranda without charge after nine hours, the maximum detention time allowed under the law. They confiscated Miranda’s electronic equipment, including his mobile phone, laptop computer, camera, memory sticks, DVDs and game consoles.

Greenwald has written a series of stories, mainly for the British Guardian, exposing the mass surveillance programs carried out by the US National Security Agency (NSA), based on documents given to him by former NSA contractor Edward Snowden. Along with Snowden, Greenwald has become a target for attacks by US politicians and media figures. Two months ago, David Gregory, the moderator of NBC News’ “Meet the Press” program, asked Greenwald in the course of an interview why he should not be prosecuted, along with Snowden, under US espionage laws.

The Guardian has also published articles about blanket electronic surveillance carried out by Britain’s General Communications Headquarters (GCHQ).

Miranda had spent the previous week visiting Laura Poitras, an American documentary filmmaker who has been helping to publish information provided by Snowden about the NSA’s illegal spying programs. According to the New York Times, Greenwald said that Miranda had gone to Berlin to give Poitras documents related to Greenwald’s investigation into US government surveillance, and Poitras had given Miranda documents previously provided by Snowden to pass on to Greenwald. Those documents, stored on encrypted memory sticks, were among the items seized by British officials.

Miranda was stopped at 8:05 Sunday morning, local time, and informed that he was to be questioned under Schedule 7 of Britain’s Terrorism Act 2000. The law, which applies only to airports, ports and border areas, allows officers to stop, search, detain and question people without probable cause and without permitting them to first obtain legal counsel. It is a crime to refuse to cooperate with the interrogators.

The Guardian reported Sunday that, according to official figures, over 97 percent of interrogations under Schedule 7 last less than one hour, and only one in 2,000 people retained are kept for more than six hours.

London’s Metropolitan Police Service, which had jurisdiction over the detention, issued a perfunctory statement saying that Miranda had been lawfully detained under the Terrorism Act. “Holding and properly using intelligence gained from such stops is a key part of fighting crimes, pursuing offenders and protecting the public,” the statement declared.

The British Home Office refused to comment on the case. A spokesman for the British Foreign Ministry said the incident was a “police matter” and would provide no further comment.

“This is a profound attack on press freedoms and the news gathering process,” Greenwald told the Guardian. “To detain my partner for a full nine hours while denying him a lawyer, and then seize large amounts of his possessions, is clearly intended to send a message of intimidation to those of us who have been reporting on the NSA and GCHQ. The actions of the UK pose a serious threat to journalists everywhere.

“But the last thing it will do is intimidate or deter us in any way from doing our job as journalists. Quite the contrary: it will only embolden us more to continue to report aggressively.”

The New York Times quoted Greenwald as saying, “The only thing they were interested in was NSA documents and what I was doing with Laura Poitras. It’s a total abuse of the law… This is a serious, radical escalation of what they are doing.”

In a separate article Greenwald posted Sunday on the Guardian web site, the investigative journalist wrote: “It’s bad enough to prosecute and imprison sources. It’s worse still to imprison journalists who report the truth. But to start detaining the family members and loved ones of journalists is simply despotic. Even the Mafia had ethical rules against targeting the family members of people they felt threatened by. But the UK puppets and their owners in the US national security state obviously are unconstrained by even those minimal scruples.”

Greenwald is absolutely justified in alleging US collusion in the detention of his partner by British authorities. The two governments have marched in lockstep in carrying out pervasive and illegal spying on their own populations and people all over the world, and in witch-hunting Snowden and others who have exposed their criminal activities, such as WikiLeaks founder Julian Assange and American Private Bradley Manning.

The detention and interrogation of David Miranda is a brazen attempt to harass and silence Greenwald and intimidate other journalists from publishing leaked material about government secrets and crimes. It shows, moreover, how antiterror laws, and the so-called “war on terrorism,” are increasingly being used to suppress political dissent and attack democratic rights.

A spokesman for the Guardian, which had paid for Miranda’s trip, said the newspaper was “dismayed” by the episode and was “urgently seeking clarification from the British authorities.”

The Brazilian government protested the detention of Miranda. The Foreign Ministry issued a statement saying: “This measure has no justification since it involves an individual against whom there are no charges that can warrant the use of this legislation.”

Widney Brown, Amnesty International’s senior director of international law and policy, said the detention of Miranda was retaliation for his partner’s role in “revealing the truth about the unlawful nature of NSA surveillance.” He continued: “He [Miranda] was detained under a law that violates any principle of fairness and his detention shows how the law can be abused for petty, vindictive reasons… The only possible intent behind this detention was to harass him and his partner, Guardian journalist Glenn Greenwald, for his role in analyzing the data released by Edward Snowden.”