In mid-December the Palestine Solidarity Campaign (PSC), a campaigning organisation in Britain supporting Palestinian issues, filed a claim in England's High Court challenging regulations issued by the British government prohibiting local government pension schemes from pursuing boycotts, divestment or sanctions (BDS) against foreign nations as part of their investment policies.

It is clear to most observers that these regulations are intended to prevent boycotts of Israel, although they do not state this explicitly.

PSC has argued that the regulations prohibit freedom of expression, are so unclear as to be unlawful, are contrary to European Union law governing pensions, and that central government has abused its powers to regulate pensions to achieve other, unrelated objectives.

The government must formally respond to PSC's claims and then the court will decide whether to grant permission for a hearing of the case.

The campaign against BDS

In fact, the pensions regulations are the latest in a series of measures taken by governments in Europe and North America to counter BDS, after Israel created a special task force with a budget of around $25.5m in June 2015, to fight the movement worldwide.

In February 2016, the British government issued guidance prohibiting pro-BDS policies in public procurement, reportedly after lobbying by the Israeli embassy in London.

Meanwhile, the United States has issued a plethora of anti-BDS laws prohibiting state investment in entities that boycott Israel.

France has also used existing hate speech laws to prosecute activists encouraging BDS, and Canada, which signed a "memorandum of understanding" with Israel in 2015 to combat BDS, has threatened to use hate speech laws against activists.

Pro-Israeli NGOs in the United Kingdom and the US have promoted legal cases against organisations supporting boycotts of Israel, often claiming that BDS constitutes a form of anti-Jewish discrimination.

The right to freedom of expression

There is clearly a concerted, official pro-Israeli campaign to crush BDS. In response, the movement and its supporters have emphasised that BDS advocacy is protected by the right to freedom of expression, just as the campaign against apartheid South Africa was, and a letter signed by some 200 legal experts on December 9, 2016 has affirmed this principle.

Indeed, the right to free speech is an important legal foundation for the movement, which protects advocacy in support of its aims and the rights of persons to engage in boycotts of Israel. Thus, court cases against BDS have been successfully defended by asserting the right to freedom of expression.

In Scotland in 2010, for example, a protest which disrupted a recital of the Jerusalem String Quartet was held to constitute a legitimate exercise in freedom of expression.

Irrespective of how the movement chooses to fight the campaign against it, the fact remains that BDS has the moral high ground: its goals are rooted in international law and the achievement of human rights by peaceful means, whereas the campaign against it is fighting to eradicate a non-violent movement with humanitarian aims.

In England in 2013 the University and College Union successfully countered a Jewish member's claim of racial harassment when a debate for an academic boycott was held to be part of the right to free speech (PDF).

In 2016, a pro-Israel NGO's case against three pro-BDS city councils in Britain was also dismissed on similar grounds.

This is not a complete answer to the threats facing the BDS movement, however, since, firstly, governments determined to pursue a political agenda to stop its activities may simply violate the right to freedom of expression.

An example was the use of the criminal law in France to prosecute 12 activists for calling for a boycott of Israeli goods when such activism should have been protected by the right to free speech.

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Laws by state legislatures in the US to divest state funds from entities that support BDS - effectively thereby imposing a penalty for the "wrong" political opinion - may also violate constitutional rights to freedom of expression.

Secondly, even when anti-BDS measures that violate free speech can be overturned by courts, they often still have a "chilling effect" on BDS advocacy, for fighting them embroils campaigners in lengthy litigation which drains their emotional and financial resources.

Indeed, the mere threat of legal action can prevent organisations supporting BDS. For instance, in 2015 the board of the GreenStar Natural Foods Market cooperative in the US reportedly refused to allow its members to vote on boycotting Israeli goods since it feared that approving the boycott could lead to litigation.

Finally, the right to freedom of expression does not give BDS comprehensive protection. For example, if public bodies in Britain were to implement a blanket boycott of Israeli suppliers in public procurement, they might be considered to be in breach of free trade rules prohibiting discrimination on grounds of nationality, and would not be able to invoke a right to free speech to defend their actions.

The need for a legal strategy

Although BDS advocacy is solidly based on the right to freedom of expression, which should continue to be asserted, it is not sufficient on its own to defend the movement. A broader legal strategy is needed here, which should include the following measures.

Firstly, significant resources need to be allocated to provide legal assistance to campaigners and organisations subject to anti-BDS legislation or legal action by pro-Israel groups to help them to defend themselves.

Secondly, initiatives are needed to design and implement BDS policies in ways that do not violate existing laws - particularly where blanket boycotts could breach regulations prohibiting discrimination on the basis of nationality.

And thirdly, the law should be used to make the case proactively for BDS, rather than simply defend it from attack.

For example, one of the goals of BDS is to persuade governments to ban trade with Israeli settlements, since all states, except Israel, consider settlements illegal. There are good legal arguments that trading with settlements is, in itself, illegal and should therefore be prohibited.

Although the BDS movement has put forward some good arguments in this respect, these could be developed further and promoted more actively.

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But in the end, and irrespective of how the movement chooses to fight the campaign against it, the fact remains that BDS has the moral high ground: Its goals are rooted in international law and the achievement of human rights by peaceful means, whereas the campaign against it is fighting to eradicate a non-violent movement with humanitarian aims.

BDS activists should take courage from this fact and use all legal means to assert their right to engage in BDS advocacy and resist the measures trying to suppress them.

Salma Karmi-Ayyoub is a barrister and legal consultant for the Palestinian human rights organisation Al Haq.

The views expressed in this article are the author's own and do not necessarily reflect Al Jazeera's editorial policy.