A U.S. Border Patrol agent checks a car on the I-93 southbound lane on Wednesday, September 28, 2017 south of the Route 175 exit south of Lincoln. Geoff Forester

U.S. Customs and Border Protection is planning five more immigration checkpoints along Interstate 93 this year, following a three-day stop over the Memorial Day weekend, according to emails from state police.

In a thread of emails released in response to a right-to-know request by the American Civil Liberties Union of New Hampshire, state police said they were informed on April 27 about the planned stops.

“Border Patrol told me today that they are planning on conducting six checkpoints this year, the first of which will be memorial day weekend,” wrote Lieutenant Gary Prince.

A spokeswoman for Customs and Border Protection, Stephanie Malin, declined to confirm the details.

“The locations and frequency of our tactical immigration checkpoints are law enforcement-sensitive and not something we share,” she said Wednesday.

If the checkpoints take place as planned, they would represent an escalation of the federal agency’s motor vehicle stops in New Hampshire, which have stirred controversy in the last year.

In August 2017, the border agents carried out the agency’s first checkpoint since 2012, blocking southbound traffic on I-93 in Woodstock and checking drivers for American citizenship. They followed it with a second traffic stop in September.

Agency representatives say the checkpoints are not a result of a change of policy, but rather an increase in funding for border protection measures under the Trump administration. The U.S. Supreme Court has upheld the agency’s authority to conduct checkpoints within 100 miles of a land or sea border, an area that encompasses most of New Hampshire.

But civil libertarians have objected to the use of drug-sniffing dogs during the searches. The federal agency has said the dogs are used to identify human smuggling, but the dogs are also trained to identify narcotics, and during a checkpoint last year 32 U.S. citizens were arrested by Woodstock police on drug offenses.

On May 1, a state circuit court judge in Plymouth ruled that those arrests demonstrated that the primary purpose of the checkpoints “was the detection and seizure of drugs,” and not immigration deterrence, making the drug arrests unconstitutional.

During this past weekend, the Woodstock Police Department was not involved and no drug-specific arrests were made – though some drugs were found and seized by the federal agents, according to Malin.

Still, the ACLU has raised concerns. In addition to its right-to-know requests against New Hampshire departments, the organization plans to submit a Freedom of Information request to the federal agency this week, according to Gilles Bissonnette, state legal director for the ACLU.

“We think that conducting an investigation as to this checkpoint is critical because we already know that the way they’ve historically conducted these checkpoints is in violation of the Constitution,” he said, referring to the May 1 decision.

“We think it’s prudent to get a handle on what exactly transpired this past weekend,” he added.

Just how state police plan to be involved with the checkpoints – if at all – in the wake of the court decision is unclear.

“I anticipate that we would conduct business as usual, but I just want to make sure I am on the right page,” Prince said in an April 27 email.

Major Matt Shapiro addressed the uncertainty: “The guidance on Border Patrol checkpoints is the same,” he wrote May 2. “We are not going to be involved in the planning, preparation, or facilitation of such checkpoints. But that being said, we will answer calls for service from Border Patrol like any other customer.”

In presenting the need for the New Hampshire checkpoints, Swanton Sector Acting Chief Patrol Agent Robert Garcia has invoked national security, calling it “a critical enforcement tool for the enforcement of our immigration laws” and a “a part of our defense in depth strategy.”

Research suggests the public doesn’t mind either. A Nov. 16 Granite State Poll from the University of New Hampshire found that 70 percent of respondents were in favor of the use of checkpoints within New Hampshire, even if those checkpoints were used to investigate drug smuggling. That included 48 percent of Democratic respondents and 90 percent of Republicans.

But to Bissonnette and other critics, the checkpoints remain a threat to both civil liberties and the state’s reputation.

“These checkpoints are bad for New Hampshire,” he said. “These checkpoints make New Hampshire look like a police state, on a holiday weekend that is popular for tourists. ... We think these experiences fly in the face of what it means to live in a free society where you don’t have to answer to federal agents as you are going about your personal business.”

(Ethan DeWitt can be reached at edewitt@cmonitor.com, or on Twitter at @edewittNH.)