Máiread Maguire, the Nobel Peace Prize laureate, will appear in court in Israel today to appeal against a deportation order.
If her appeal is unsuccessful the activist will be barred from Israel for ten years.
Ms Maguire arrived in Israel on September 28 but was denied entry at Ben Gurion airport because she had been deported in June for trying to breach the naval blockade and reach the Gaza Strip by boat.
The ship, known as the Rachel Corrie, was boarded by the Navy and redirected to Ashdod.
At the time, Ms Maguire gave written confirmation that she would not attempt to enter Israel again. But when she landed in Israel the Belfast activist, 66, refused to cooperate with security officials and blocked the gangway of the plane.
Her lawyers won a temporary injunction, but on Friday a court rejected this and gave her 48 hours to leave the country.
The state’s representative, Hani Ofek, said two letters had been sent to Ms Maguire in advance warning her that she would not be allowed into Israel.
Mr Ofek said: “[She] decided to take the law into her own hands and establish facts on the ground by showing up at Ben-Gurion, apparently thinking that such an act would give her an advantage and lead to her being allowed to enter Israel, contrary to the law and the deportation orders against her.”
A Foreign Ministry official added: “Ms Maguire had deliberately chosen to take part in an illegal clash with Israeli authorities.
“This unfortunate, self-imposed situation now makes it impossible for us to intervene in favor of changing Ms. Maguire’s legal position in the eyes of Israeli law.”
The court is expected to come to a decision today.
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