As Israel expanded its control and occupation over four territories in the aftermath of the Six Day War, it devised a system of population control that remains in place five decades later.

After the 1967 war, the Israeli military declared the occupied territories to be closed areas, making it mandatory for Palestinian residents to obtain permits to enter or leave. Palestinians who were abroad during that time missed out on the subsequent population census and were not granted identification papers.

The clear delineator that has separated and dictated the lives of these Palestinians is the colour-coded identification system issued by the Israeli military and reinforced in 1981 through its Civil Administration branch. Palestinians in the occupied West Bank and the Gaza Strip have green IDs - generally issued once they turn 16 - while Palestinians in East Jerusalem and Israel have blue IDs.

The cards affect everything from freedom of movement to family unity.

Tool of control

IDs are still issued by the Israeli military, despite the 1993 arrival of the Palestinian Authority government, noted Tahseen Elayyan, head of monitoring and documentation for the Palestinian rights group Al-Haq.

"When it comes to the West Bank and Gaza Strip IDs, the role that the PA plays is more of a secretarial role, such as printing them out," he told Al Jazeera. "Ultimately, it is the Civil Administration in the Bet Il settlement who decides to issue them, based on whether the Palestinian is included in the population census."

Miriam Marmur, international communications coordinator for the Gisha human rights organisation, said that Israel's control of the Palestinian population registry has been central to its efforts to control movement and demographics in the occupied Palestinian territories.

"Power over Palestinians' residency status is used as a tool of control," she said. "Palestinians must be included in the Palestinian population registry to obtain ID cards and passports."

In the occupied West Bank, Marmur added, Palestinians must have their IDs for internal travel, due to the checkpoints interspersed within the territory.

This system has drawn comparisons to laws in apartheid South Africa designed by whites to control the movement of blacks and mixed-race people and to keep them in inferior positions.

'Separation is the rule'

Freedom of movement for Palestinians in the West Bank and Gaza, especially over the past 25 years, has been heavily restricted between these territories, where separation is "the rule and access is the rare exception", Marmur said.

It is illegal for a Palestinian in the occupied West Bank to travel to Gaza and Jerusalem unless they have a special travel permit from Israel. Likewise, Palestinians in Gaza are forbidden from going to Jerusalem and the West Bank unless the Israeli military issues them a permit.

"Israeli law had different military orders in the West Bank and Gaza Strip," Elayyan said. "Each territory was administered by a different Israeli military commander. The point of that was to maintain the division between the two territories, to make them easier to control."

According to Marmur, Israel has practically stopped processing requests for registration and changes of residency status since the year 2000.

"As a result, many Palestinians have been unable to choose their place of residence, as well as take up opportunities for study and work," she said.

Since that year, which was when the second Intifada broke out, students from Gaza have been forbidden from going to study in the occupied West Bank.

Family unification

These identification cards can also impinge on Palestinians' right to family unification if a husband and wife hold different ID cards.

"Palestinians from Gaza who marry residents of the West Bank cannot move to the West Bank to live with their spouses," Marmur noted.

Furthermore, Palestinian ID-holders who marry those who do not have an ID live with the risk of forced separation. Children can only be registered under one parent, not both.

A poll conducted by the Palestinian Center for Policy and Survey Research in 2013 concluded that 31 percent of Gaza residents - more than half a million people - had relatives in the occupied West Bank, East Jerusalem or Israel. Twenty-six percent of Gaza residents had relatives in the occupied West Bank.

The blue Jerusalem IDs

Freedom of movement is not as restricted for Jerusalem residents, who are granted permanent residency in the city but not Israeli citizenship. While they also need permits to go to Gaza, they can travel freely to the occupied West Bank and modern-day Israel.

However, restrictions are manifested in other ways.

"The Israelis act like giving us permanent residency in Jerusalem is a privilege, but it is more cosmetic than anything else," Dalia Nashashibi, a primary school teacher from Jerusalem, told Al Jazeera.

"Yes, we face shorter queues when crossing the Allenby border and yes, we can move from one territory to the other [except Gaza] without a permit, but we still get searched and humiliated at checkpoints," she added. "That's as far as the 'privilege' extends."

Holders of the Jerusalem IDs live under the constant threat of residency revocation. Living outside Jerusalem in the other occupied territories is considered sufficient grounds for Israel to annul a permit.

For financial and family reasons, many Jerusalemites live in the occupied West Bank, but they must maintain a house within Jerusalem's municipality to keep their residency. Israeli authorities regularly conduct random inspections of households in Jerusalem to see whether the blue ID holders actually live there.

These Palestinians must pay a hefty property tax to the municipality - in addition to the national insurance tax - yet they receive few municipal services, with their neighbourhoods severely lacking in infrastructure, health services and educational facilities.

This is all part of Israel's attempts to maintain a 70:30 Jewish-Palestinian ratio, Elayyan said.

"They lessened the number of Palestinians in the population census that were given Jerusalem IDs and added more geographical lands around the city that were used to construct Jewish-only settlements," he said.

The situation is even harder for Jerusalem ID holders who live outside the country, Nashashibi added: "If we do not come back for a visit after more than three years have passed, then our IDs are automatically cancelled. We suffer so much," she added. "The Jerusalem ID has more negatives than positives."