Human rights campaigners have prepared a federal lawsuit aiming to permanently shut down the bulk collection of billions of US phone records – not, this time, by the National Security Agency, but by the Drug Enforcement Agency.

Human Rights Watch, represented by the Electronic Frontier Foundation, filed their lawsuit in Los Angeles federal court on Wednesday morning to stop the DEA from hoovering up billions of records of Americans’ international calls without a warrant.

The reach of the program, exposed by USA Today, lasted for two decades and served as a template for the NSA’s gigantic and ongoing bulk surveillance of US phone data after 9/11.

Though US officials insist the DEA is now out of the bulk-collection business, the revelation of mass phone-records collection in the so-called “war on drugs” raises new questions about whether the Obama administration or its successors believe US security agencies continue to have legal leeway for warrantless bulk surveillance on American citizens, even as officials forswear those powers publicly.

Human Rights Watch alleges that the bulk surveillance puts its work in jeopardy.

Dinah PoKempner, Human Rights Watch’s general counsel, said in a Wednesday statement: “At Human Rights Watch we work with people who are sometimes in life-or-death situations, where speaking out can make them a target. Whom we communicate with and when is often extraordinarily sensitive – and it’s information that we wouldn’t turn over to the government lightly.”

Mark Rumold, an EFF attorney representing the human-rights group, said the government was once again stretching its surveillance authorities to the breaking point, and all in secret.

“It seems like, from the government’s perspective, the only limitation on bulk surveillance is its ability to keep it hidden from the American public. The DEA program is yet another example of the government taking a seemingly unexceptional legal authority and transforming it behind closed doors into a tool for mass surveillance,” Rumold told the Guardian.

According to a USA Today, Republican and Democratic US presidents George Bush Sr, Bill Clinton, George W Bush and Barack Obama permitted the DEA to monitor and store call data surrounding “virtually all telephone calls” from the US to 116 countries – most of the world – linked to drug trafficking. Its existence was first disclosed in January.

The program, strongly reminiscent of the continuing bulk collection of US phone data by the NSA revealed to the Guardian by whistleblower Edward Snowden, was intended to give US law enforcement the ability to track and visualize and map connections in the global flow of money and narcotics. Starting in 1992, the so-called “USTO” effort operated without judicial approval, despite the US constitution’s warrant requirement.

In a prologue to the FBI’s now-routine post-9/11 non-judicial subpoenas and the NSA’s 2001-06 operations of the bulk domestic phone records collection, the DEA would secretly demand that telecos turn over call logs – after-the-fact records documenting a phone call – in bulk.

Even as the NSA opted to place its own domestic bulk collection under a rarely-rejected-or-modified general warrant from a secret surveillance court, the DEA continued its collection unilaterally.

“We knew we were stretching the definition” of the DEA’s leeway to seek records without a court order, a former official told USA Today.

According to the paper, attorney general Eric Holder ended USTO in September 2013 out of fear of scandal following Snowden’s disclosures. Though Obama pledged greater transparency on surveillance from the outset of the Snowden revelations, Holder, who had first backed USTO as a Clinton administration deputy attorney general, shut it down in secret.

While Snowden did not expose USTO, several NSA programs he has exposed referenced the DEA as an NSA partner, giving the DEA another secret pathway to massive amounts of US communications records. Lawyers have suspected that the warrantless bulk records collection provides prosecutors the ability to enter into evidence incriminating material that could otherwise be thrown out of court for its inadmissible origins.

Although a Justice Department spokesman told USA Today that the DEA is “no longer collecting bulk telephony metadata from US service providers,” lawyers for Human Rights Watch are less than convinced that assurance sufficiently portrays the scope of US dragnet surveillance.

“There’s no reason to think that the US government is out of the bulk surveillance business. But that’s exactly what we’d like to establish with this suit – a ruling that confirms, once and for all, that bulk surveillance of Americans’ records is unconstitutional,” Rumold said.

The warrantless bulk phone records collection, though cited by former officials as a valuable tool, has not stopped the upward growth of domestic narcotics consumption. In 2012, according to the National Institutes of Health, 9.2 % of Americans had consumed an illicit or controlled substance in the past month, up from 8.3% a decade earlier. Repeated studies have shown that enforcement of drug laws disproportionately impacts black and Hispanic Americans despite white people’s comparable rates of marijuana consumption.

Abroad, the US spends billions on drug eradication, with marginal results. More than $9bn since 2000 has gone to aid Colombia’s fight against narco-traffickers alone. In Afghanistan, the US has spent more than $7.5bn over more than a decade to stem the tide of Afghan narcotics, yet opium poppy cultivation has only risen.

On Tuesday, Rand Paul, the libertarian Kentucky senator, announced his bid for the Republican presidential nomination. A central aspect of Paul’s candidacy is a pledge to end “on day one” the bulk collection of Americans’ phone records.