UNITED NATIONS -- The rejection by a Belgian appeals court of war crimes charges against Israeli prime minister Ariel Sharon was "regressive" and should be overturned by Parliament, Human Rights Watch said Thursday.

"We feel that was a very regressive decision that contradicts not only Belgian law but also Belgian practice since that law was adopted in 1999," HRW lawyer Richard Dicker told a news conference.

On Wednesday, the indictment chamber of the Brussels Appeal Court threw out a lawsuit over Sharon's role in the 1982 massacres of Palestinians in the Sabra and Shatila refugee camps in Lebanon.

The court ruled that the suit, brought by 23 survivors of the massacre, was inadmissible because Sharon was not in Belgium when it was lodged a year ago, AFP reported.

The Palestinians' case was based on a so-called "law of universal competence" that enables Belgian courts to try persons for alleged war crimes, crimes against humanity or genocide that took place outside Belgium.

"For cases based on universal competence ... it is necessary that the alleged perpetrators be in the territory of the kingdom (of Belgium). Otherwise they are inadmissible," a court spokesman said.

Dicker said that HRW was confident that if this decision was not overturned in a higher court, "the lawmakers of Belgium will go forward with a new, much more explicit piece of legislation." Sharon was Israel's defense minister when Israeli-allied Christian militias entered Sabra and Shatila in September 1982, killing between 800 and 2,000 Palestinian refugees.

The massacre coincided with an Israeli invasion of Southern Lebanon and Sharon was later forced to resign from office over the incident.