An independent US executive-branch board has concluded that a major National Security Agency (NSA) surveillance programme targeting foreigners overseas is lawful and effective but that certain elements push "close to the line" of being unconstitutional.
The "unknown and potentially large" collection by the agency of e-mails and phone calls of Americans who communicate with foreign targets was one aspect that raised concerns, the Privacy and Civil Liberties Oversight Board said in a report released online on Tuesday.
But the board did not go as far in its recommendations as privacy advocates would like. For instance, it would leave in place the government's ability to conduct warrantless searches for Americans' communications in the data gathered by the NSA.
At issue is a programme authorised by Section 702 of the Fisa Amendments Act of 2008, which was an effort to bring under the law a surveillance effort started after the 2001 terrorist attacks and run exclusively by the executive branch.
Under the law, the government can target "non-US persons reasonably believed to be located abroad". However, it is not required to obtain individualised warrants, even though the collection is done inside the United States.
The 191-page report comes after a year of heightened debate and scrutiny over US surveillance practices in the wake of leaks of NSA documents to journalists by former agency contractor Edward Snowden.
In January, the board issued a strongly worded report that concluded that a different NSA programme involving the collection of Americans' phone call records was illegal and should end. The agency's gathering of billions of such "metadata" records - numbers dialed, times and durations - did not comply with the law, the board found.
It also had enabled the government to obtain a greater range of foreign intelligence than it otherwise would be able to, and to do so quickly and effectively, the board said. It also said the programme had led the government to identify previously unknown individuals involved in international terrorism.
But certain features raised privacy concerns, the board said. For instance, though the law does not explicitly permit it, the agency collects communications in which a target's e-mail address or phone number is mentioned - even if it is in the body of an e-mail as opposed to the "to" or "from" line.
As a result of this practice, known as "about" collection, both parties to the communication could be US persons or inside the United States. This was largely due to technical difficulties with determining the location of the parties at the time of collection, the board said.
Also of concern was the use of queries to search for the communications of specific US persons within the database of information already gathered. Sometimes called "backdoor searches", the practice was the target of a House of Representatives vote last month to bar such searches.
The board was divided on the issue. Two members recommended court approval - but with less than a warrant based on probable cause. Two members said sign-off by an executive-branch agency was sufficient. And a fifth declined to weigh in.
"The board's recommendations are surprisingly anaemic, particularly in light of its much more robust approach in its January report on the bulk collection of Americans' telephone records," said Elizabeth Goitein, co-director of the Brennan Centre for Justice's Liberty and National Security Programme.
The board also recommended, among other things, that the NSA's targeting procedures be revised to specify criteria for determining the expected foreign intelligence value of a particular target. And it urged that the NSA annually count the number of phone calls acquired in which one caller is located in the United States, the number of e-mails that originate or terminate in the United States and the number of queries performed for US persons' data.