An Israeli-Arab politician who took part in a flotilla attempting to breach the blockade of Gaza in 2010 will be able to compete in the general election in three weeks after the supreme court unanimously overturned a ban on her candidacy.

A panel of nine judges overruled a decision by the central elections committee to disqualify Haneen Zoabi from seeking re-election as a member of the Israeli parliament. The committee's decision was based on her participation in the flotilla.

Following the supreme court's ruling on Sunday, Zoabi said the attempt to bar her from the election was "the result of political and personal persecution against me, against my party and against the Arab public as a whole".

But, she added: "This ruling does little to erase the threats, delegitimisation and physical as well as verbal abuse that I have endured … over the past three years."

Zoabi, a member of the Israeli-Arab party Balad, was elected to parliament almost four years ago. In May 2010, she was a passenger on the Mavi Marmara, on which nine Turkish activists were killed by Israeli commandos intent on stopping the flotilla reaching Gaza.

She later had her parliamentary privileges revoked but an attempt to bring criminal charges against her failed. She was assigned special protection after receiving death threats.

Last month she spoke out against the Israeli offensive on Gaza, saying Israel was breaking international law and "no military force can crush the people's survival instinct".

After a supreme court hearing last week against the disqualification, Zoabi was heckled and jostled by around 30 rightwing activists outside the court, forcing her to take shelter until security guards cleared the area.

The court did not issue reasons for its ruling, but will issue a detailed judgment at a later date. Israel's attorney-general said there was insufficient evidence to disqualify Zoabi.

Attempts during previous election campaigns to disqualify Israeli-Arab candidates have also been overturned by the supreme court. Israeli-Arabs make up 20% of the country's 7.8 million population, and there are currently 11 members of the 120-seat parliament representing Israeli-Arab parties.

Following Sunday's ruling, Zoabi's lawyer, Hassan Jabarin said: "The fact that the repeated attempts to disqualify Arab [members of parliament] and political parties made over the last 15 years have had no legal basis, as the Israeli supreme court has consistently ruled, indicates that the aim of the rightwing is to de-legitimise the elected Arab leadership in Israel.

"The case of Haneen Zoabi differs from the others in that an attempt was made to dehumanise her and to attack her personally as a woman. She was also branded as a terrorist simply for participating in the Gaza freedom flotilla, which was a legitimate political act, and even though she has not been indicted for any crime."

Likud-Beiteinu, the rightwing alliance headed by the prime minister, Binyamin Netanyahu, said it would amend the law in the next parliamentary term to "clearly state that anyone supporting terror is automatically disqualified" from being a member of parliament.

Other politicians who backed the move to disqualify Zoabi spoke of their regret at the supreme court's decision. Danny Danon, who presented an 11,000-signature petition to the elections committee demanding Zoabi's candidacy be banned, said: "Today the court decided to back the Marmara's terrorist instead of the navy commandos … Zaobi belongs in prison."