Rights groups and Palestine advocacy organisations have blasted a Maryland executive order that bars state contracts for firms that boycott Israel as part of a "legislative assault" that targets the Palestinian-led Boycott, Divestment and Sanctions (BDS) movement.

On Monday, Maryland Governor Larry Hogan signed the executive order (pdf), which accuses firms that boycott Israel of posing "undue risks as contracting partners".

Surrounded by leaders of pro-Israel groups and Jewish organisations, Hogan addressed a press conference after signing the order.

"There is no place in our state for boycotts and threats," he said, as reported by the Baltimore Sun.

At the time of publication, Hogan's office had not replied to Al Jazeera's request for comment.

Brian Hauss, a staff attorney at the American Civil Liberties Union (ACLU), described the governor's order as "part of a legislative assault we've seen over the past few years on the right to boycott", citing a string of legal measures in states across the US.

Speaking to Al Jazeera by telephone, he described the measure as "blatantly unconstitutional", referring to the US Constitution's First Amendment, which guarantees the freedom of expression.

BDS is a global campaign that was launched in 2005 with the intent of holding Israel accountable for violations of international law and Palestinian human rights.

Drawing from the anti-Apartheid struggle in South Africa, the movement calls for boycotting, divesting from and sanctioning Israel until it ends its decades-long occupation of Arab land, provides Palestinian citizens of Israel with full equality and allows Palestinian refugees to return to their homes.

Wave of legislation

In recent years, the movement has grown in the US, particularly on university and college campuses. In response, pro-Israel organisations have lobbied for measures that target students and state bills alike.

Throughout the last two years, at least 22 states have passed laws or implemented executive orders that target BDS activism.

"These laws are examples of the state leveraging financial resources to coerce people to move away from political movements the state does not favour," Hauss said.

"Whatever you think about the BDS movement, there is clear evidence of government viewpoint discrimination," he added.

"That's something that the First Amendment clearly prohibits."

Last week, Dickinson, a city in Texas, posted an application for hurricane relief funds that mandated applicants to sign an agreement promising they will not boycott Israel. The city cited a Texas law that prohibits state agencies from contracting companies that boycott Israel.

The move prompted widespread condemnation from rights groups, including the ACLU.

{articleGUID}

In July, North Carolina Governor Roy Cooper signed a law that prohibits state agencies from doing business with companies that engage in BDS.

A month earlier, Kansas Governor Sam Brownback signed HB 2409, a similar law which requires both state-contracted individuals and companies to provide a written certificate proclaiming that they are not participating in a boycott of Israel.

Earlier this month, the ACLU filed a federal lawsuit challenging the Kansas law on behalf of Esther Koontz, a public high school teacher who advocates a consumer boycott of Israeli products and international goods produced in illegal Israeli settlements in occupied Palestinian territory.

'Chilling effect'

Jack Saltzberg, executive director of the Israel Group, an organisation that lobbies against BDS, argued that anti-BDS legislation has "nothing to do with curbing free speech".

"It is generally legislation that constricts governmental institutions and beneficiaries from divesting from Israel, or at least following certain guidelines," he told Al Jazeera.

"Therefore, when passed by a state, students in that state's universities can freely say anything they want about Israel, or even vote to divest from Israel."

Rahul Saksena, a staff attorney at the US-based Palestine Legal, said that the wave of anti-BDS laws is designed to intimidate Palestine solidarity activists by creating a "chilling effect".

Speaking to Al Jazeera by telephone, Saksena explained that the host of laws and bills follow in the tradition of anti-Palestinian measures that have targeted student activists in recent years.

Those measures include banning advocacy groups like Students for Justice in Palestine and suppressing pro-Palestinian protests and educational activities.

In May 2015, Canary Mission, a pro-Israel website, was created to track Palestine solidarity activists and dash their future employment prospects.

Since 2015, however, pro-Israel advocacy organisations have increasingly focused their efforts on supporting anti-BDS legislation, according to Saksena. Most of the legislation, he said, has enjoyed the support of both the Republican and Democratic parties.

The problem is that boycotts for Palestinian rights, like all boycotts, are protected by constitutional rights. Rahul Saksena, staff attorney at Palestine Legal.

Saksena said efforts to stifle Palestine solidarity activism are evidence that pro-Israel organisations are unable to make their case on moral grounds.

"What's behind [this] is an unwillingness to confront the issue of Palestinian rights on its merits," he said. "Instead, they want to silence the conversation."

He added: "Rather than engaging in the conversation and having a debate about human rights abuses and violations of international law, they pour resources into pressuring universities and lawmakers to shut down the conversation."

Earlier this year, the federal Israel Anti-Boycott Act - a bill that seeks to criminalise boycotting Israel - was introduced in both the US House of Representatives and the Senate.

Signed by at least 100 civil society groups and human rights organisations, a joint statement published in August called on Congressional legislators to oppose the Israel Anti-Boycott Act.

Saksena said: "The problem is that boycotts for Palestinian rights, like all boycotts, are protected by constitutional rights."