The Helou family is so worried about getting expelled to Gaza by Israeli authorities that they're all but trapped in this West Bank town. They couldn't even leave to get their disabled son the best possible surgery to let him walk.

Some 20,000 Palestinians in the West Bank live under the same fear, because they hold residency papers from the Gaza Strip and Israeli authorities refuse to allow their papers to be updated — though they have lived in the West Bank for years.

Israel eased its blockade on the Hamas-run Gaza Strip this month by allowing more goods into the territory. But the embargo is just one of the many restrictions imposed on Palestinians and their movement — including rules effectively locking them into whichever of the two, widely separated territories they were born in, the West Bank or Gaza.

Fears of families like the Helous that they'll be thrown out of their homes have only increased since recent Israeli military rules branded those living in the territory without residency papers as "infiltrators" subject to prison or expulsion. The rules enshrine the military's on-and-off policy for the past decade.

Moving within the West Bank runs the risk of running into the more than 500 Israeli military checkpoints that carve up the tiny territory — about the size of Connecticut — and being discovered by soldiers.

"The whole world is closed to my children," said Lubna Helou, whose eldest son Issam, 17, has not walked for years because of an extreme flat foot condition.

His parents were afraid to send him abroad for surgery because he would have to show Israeli soldiers his ID that lists his address as Gaza, exposing him to the risk of expulsion. They've also skipped doctor's appointments outside his small town of Jenin.

"Tens of thousands of people are under constant threat, preventing them from obtaining jobs, medical care, educational opportunities — for fear of crossing a checkpoint," said Sari Bashi of the Israeli rights group Gisha, which is challenging the military order in court.

Israeli military officials say Gaza residents can return to that territory along with their West Bank spouses. But that would mean leaving West Bank homes they have lived in for years. Moreover, most Palestinians are reluctant to settle in impoverished Gaza, where daily life is a formidable struggle. The Islamic militant group Hamas seized Gaza by force in 2007, while its rival, the U.S.-backed Fatah movement, continues to run the West Bank.

The regulations were first imposed in 2000 after the eruption of the last major round of Israeli-Palestinian fighting. Israeli officials sought to restrict the mobility of gunmen or bombers sneaking into Israel to carry out attacks.

The fighting, which lasted for about five years, "was a security turning point for Israel," said military spokeswoman Lt. Col. Avital Leibovitch. More than 5,000 Palestinians and upwards of 1,000 Israelis were killed during the period.

The rules meant that Palestinians could no longer move freely between the West Bank, Gaza and east Jerusalem, the areas Israel captured in the 1967 Mideast war, and which Palestinians want for their future state.

Thousands of Gazans who moved to the West Bank before 2000 could no longer register their new address in their Israeli-issued IDs. The two territories are located on opposite sides of Israel, and the only way to get from one to the other is to go through Israel. Also, West Bankers were required to get special permits to join spouses in nearby east Jerusalem.

In contrast, Israeli Jews may freely live in east Jerusalem and in West Bank settlements.

Gisha, the Israeli rights group, argues a person's address shouldn't be treated like a nationality. They also argue that the policies violate international law and Israel's own signed agreements with Palestinians to treat the West Bank and Gaza as one political unit — not two separate territories.

Since restrictions began in 2000, Israel agreed to transfer the residency permits of just 17 Gaza residents to the West Bank, Palestinian officials said.

The Helous started out in Gaza. Gaza-born Mouin, 41, and his wife, Lubna, 35, a West Bank native, had four children in Gaza. In 1998, they crossed to the West Bank town of Jenin, where their four youngest children were born.

Now the Helou family is trapped. Issam, the eldest, was operated on by a local surgeon in Jenin in March. Since then, his legs have been encased in plaster and he's on a constant dose of pain killers. His doctor says the prognosis is good.

Issam's mother says doing the surgery locally, where prospects for success were much lower, was the family's only practical option for getting Issam to walk again.

Some families have already been cleaved apart.

Gaza-born Baker Hafi, 37, had lived in the West Bank for a decade when he was picked up by Israeli soldiers at his home for questioning on security-related suspicions. He was released without charges and dumped into Gaza in January. He hasn't seen his wife or their two baby girls since. "I speak to my wife on the phone and look at her picture. That's our relationship right now," Hafi said.

The March military order sparked fears of a move to expel Gazans in large numbers, but there has been no noticeable increase.

Leibovitch, the army spokeswoman, said the order was intended to clarify military policies. She said only those Gaza residents found by patrolling Israeli soldiers would be expelled — some 90 people in the past two years.

Wafa Abdel Rahman of Harakeh, a newly formed Palestinian group lobbying to overturn the rules, argues military officials should rectify the unfair rules instead of leaving Palestinians at the army's whim.

"We don't think the Israelis have innocent intentions," she said.