Lara Alqasem, a 22-year-old graduate student from Florida, had been detained at Tel Aviv's Ben-Gurion Airport for more than two weeks as she appealed a decision to deport her.
Israeli authorities allege that she called for a boycott of Israeli goods and that they could deny her entry under a recently-passed law.
Israel's High Court of Justice ruled in Alqasem's favor on Thursday, and her attorneys said she subsequently left the airport and entered Israel.
In a statement issued late Thursday, Alqasem thanked her attorneys and supporters.
"I'm relieved at the court’s decision and incredibly grateful for the work of my amazing and tireless lawyers Yotam Ben-Hillel and Leora Bechor as well as the support of my family and friends," she said. "I will be happy to say more when I've had a chance to rest and process."
For their part, her lawyers said they were heartened by the decision, which Israeli prosecutors said on Thursday that they would not appeal.
"The Supreme Court's decision is a victory for free speech, academic freedom, and the rule of law," her lawyers, Leora Bechor and Yotam Ben-Hillel, said in a statement. "Israel has the right to control its borders, but that right does not give the Ministry of Interior unchecked power to turn away anyone it deems unwanted."
They added that Alqasem's appeal "has ensured that no one else should be denied the right to enter Israel based on sloppy Google searches and dossiers by shadowy smear groups."
They called her case a "gross misapplication of the law."
For their part, Israeli officials expressed disappointment in the ruling.
"I am deeply saddened by the Supreme Court's decision, which indicates a lack of understanding of the methods of action of the BDS organizations, and damaged the State of Israel's ability to fight the boycott activists who harm all of us," said Gilad Erdan, Minister of Internal Security and Strategic Affairs, referring to her alleged support for the Boycott, Divestment and Sanctions movement, known as BDS, which advocates boycotts as a political tool to protest Israeli policies related to the Palestinian territories.
Alqasem had intended to study at Hebrew University in Jerusalem, which had joined her appeal. She had been held at Ben-Gurion Airport since she landed there on Oct. 2, pending her appeal.
A recently passed Israeli law allows authorities to ban entry to anyone it deems to have held a senior position in an organization publicly calling to boycott the State of Israel.
Alqasem is a former president of the University of Florida chapter of Students for Justice in Palestine -- which an Israeli minister labeled an extremist organization -- and is from the Ft. Lauderdale area of Florida, according to the Associated Press.