JERUSALEM, Feb 8 (Reuters) - Israel's Supreme Court ordered two pro-Palestinian foreign activists released on bail on Monday, saying Israeli immigration officers overstepped their bounds by detaining them in the West Bank.

Their lawyer described their arrest as part of a campaign by Israeli authorities to choke off weekly demonstrations by Palestinians, left-wing Israelis and foreign activists against Israel's West Bank barrier as peace efforts remain at a stalemate.

Israeli soldiers raided the West Bank city of Ramallah on Sunday and detained Spaniard Ariadna Jove Marti and Australian Bridgette Chappell, handing them over to immigration officers overseen by Israel's Interior Ministry for possible deportation.

Both women belong to the International Solidarity Movement, which is at the forefront of anti-barrier demonstrations.

Palestinian authorities and the women's attorney called the entire operation illegal, arguing the military had no right to raid a city within an area designated by interim peace accords as being under Palestinian civil and security jurisdiction.

But the Supreme Court ordered Marti and Chappell released on other grounds, saying immigration officers -- authorised only to operate inside Israel -- had taken custody of the women from the military at a prison inside the West Bank.

(The immigration officers) have no authority outside the legitimate borders of Israel, the women's lawyer, Omer Schatz, told reporters before the court ordered his clients freed on bail.

The two activists were banned by the court from returning to the West Bank but told they could file an appeal against deportation from Israel, which controls the territory's borders.

Israel captured the West Bank in a 1967 war but has not formally annexed the area, which Palestinians hope to make part of a future state.

Protesters stage weekly demonstrations in various Palestinian villages against Israel's construction of West Bank walls and fences that have denied them access to their land.

Israel says the barrier, which the World Court has deemed illegal over its construction in occupied land, has stopped suicide bombers and can be removed in the future if the security situation improves.

The Israeli authorities deported a leading ISM activist last month, the organisation said. Eva Novakova, from the Czech Republic, had also been arrested in Ramallah. (Writing by Jeffrey Heller, Editing by Janet Lawrence)