The Obama administration has provided its fullest description yet of why it believes it has the authority under the Patriot Act to collect in bulk the phone records of millions of Americans without suspicion of wrongdoing.

On Friday, as President Obama gave a press conference announcing his willingness to consider reforms to the National Security Agency's bulk-collection programs, his administration released two unclassified "white papers" that Obama hailed as steps at transparency. One was a legal analysis of the bulk phone records program; the other was a generic description of the NSA's foreign-directed surveillance activities.

Neither document provided much in the way of new information for the programs: a significant amount of the legal analysis about the bulk phone records program echoed congressional testimony by NSA and Justice Department officials, especially a lengthy July speech from Robert S Litt, the top lawyer in the intelligence community. Nor was either document a dispassionate recitation of facts: both presented the administration's case for why Americans should be "comfortable" – as Obama put it today – with bulk collection of their data.

Still, the documents shed light on controversial legal theories that are likely to be tested in court in the weeks and months ahead.

The Obama administration justifies the bulk phone records collection program under Section 215 of the Patriot Act, which authorizes the government to acquire "tangible things" that are "relevant" to an investigation. Since the Guardian disclosed the existence of the bulk phone records program, thanks to the ex-NSA contractor Edward Snowden, legal scholars have puzzled over how the phone numbers dialed, lengths of calls and times of calls of millions of Americans unsuspected of terrorism or espionage meet that standard.

The administration's answer has several components. It argues in the white paper, "'relevance' is a broad standard", which can include the "reasonable grounds to believe" that when all the data is collected, "when queried and analyzed consistent with the [surveillance] Court-approved standards, will produce information pertinent to FBI investigations of international terrorism." To do this requires "the collection and storage of a large volume of telephony metadata." That is – information about your phone calls.

It further argues that a "tangible thing" can include a phone number or the length of a phone call, and contends that the legislative history of the Patriot Act indicates that Congress always intended that to be the case, despite the incorporeality of phone data, particularly when compared to say, a medical record or a receipt. "There is little question that in enacting Section 215 in 2001 and then amending it in 2006, Congress understood that among the things that the FBI would need to acquire to conduct terrorism investigations were documents and records stored in electronic form," the administration writes.

Finally comes a problem that was brought up by several members of the House Judiciary Committee during a raucous July hearing. The collection of the bulk phone data comes prior, logically, to any specific investigation. So how can the administration argue the bulk phone records collection is pertinent to any particular inquiry?

"Unlike ordinary criminal investigations," the administration replies, "the sort of national security investigations with which Section 215 is concerned often have a remarkable breadth – spanning long periods of time, multiple geographic regions, and numerous individuals, whose identities are often unknown to the intelligence community at the outset.

"The investigative tools needed to combat those threats," it continues, "must be deployed on a correspondingly broad scale."

Put differently: "If you're looking for the needle in the haystack, you have to have the entire haystack to look through," as deputy attorney general James Cole testified in July.

It is a legal theory that has attracted great opposition.

In a turn reminiscent of Marshall McLuhan's classic cameo in Woody Allen's film Annie Hall, the author of the Patriot Act is loudly telling the administration that it's misconstruing the very legal text it relies on. Representative James Sensenbrenner, a Wisconsin Republican and primary Patriot Act author, told the Guardian last month that the administration was abusing a law that has itself attracted criticism for being overbroad.

James Sensenbrenner was a primary author of the Patriot Act. Photograph: Chip Somodevilla/Getty Images

"I would advise the president to reconsider his misinterpretation of Section 215 and rein in abuse," Sensenbrenner said, before a slated expiration of the bulk phone records collection. Sensenbrenner ultimately voted to end the bulk phone records program during a dramatic House floor fight, in late July, that narrowly failed.

Underlying the administration's arguments even deeper are two contentions that are likely to face challenges in federal court.

First is a claim – well supported by numerous court cases – that "metadata" like phone records do not enjoy privacy protections under the Fourth Amendment to the US Constitution, since they amount to data that customers willfully provide phone companies. There is much legal history supporting that contention – for a single individual's phone records. There is far less legal history to support the idea that that bulk phone collection on every American phone customer does not entail a privacy violation.

In the white paper, the administration acknowledges the ambiguity. "The cases that have been decided in these contexts to do not involve collection of data on the scale at issue in the telephony metadata collection program, and the purpose for which the information was sought in [prior cited] court cases was not as expansive in scope as a nationwide intelligence collection effort designed to identify terrorist threats."

The American Civil Liberties Union and the Electronic Privacy Information Center are putting the question of a privacy right over bulk metadata before federal courts right now.

Finally, there is an idea that has gotten less attention but which administration officials have brought up to Congress. The administration contends that the surveillance does not occur when NSA collects bulk data, but only when it sifts through it.

That is why the administration spends great effort arguing that only "trained expert analysts" can study the data; that it can only access it when there is "reasonable, articulable suspicion" of a connection to a foreign terrorist organization specified by the secret surveillance court; and that adequate internal safeguards are in place by the NSA.

The question of when the surveillance occurs is an intriguing one. But civil libertarian critics point out that the Patriot Act is not a statute governing analysis of collected records; it is a statute governing the government's ability to collect the records in the first place. It is for this reason that even as the administration defends its collection/analysis distinction, senior intelligence officials declare, as a fallback plan, their willingness to abandon the phone records database so long as the phone companies store the same information.

There are other aspects of the white paper that command the attention of a surveillance wonk. The administration often dismisses fears that the government is, for instance, empowered to track the location of phone calls and other things as yet undisclosed by the Guardian. But the white paper does not rule such things out entirely. It says instead, "the government cannot, through this program, listen to or record any telephone conversations."

Or, to answer concerns that medical histories or other compromising data are fair game for collection: "This conclusion does not mean that any and all types of business records – such as medical records or library or bookstore records – could be collected in bulk under this authority."

Or: "The Government also does not collect cell phone locational information pursuant to these orders."

Much remains unclear about the full scale of the NSA's bulk surveillance efforts. It also remains unclear whether the administration will disclose more – or leave that task to journalists.