With three weeks left before balloting for a new parliament, Lebanon still has no election law, which could result in an election being held under the 2000 rules.
But there has been strong opposition to the 2000 law, drawn under Syrian control - reportedly by Syrian intelligence officers - and described by some as a recipe to bring back another pro-Syrian parliament.
Gathering near Parliament in Beirut, at least 2000 flag-waving protesters urged the legislature to act on an amnesty bill that would end Geagea's life term in prison.
Chants of "Freedom for Samir Geagea is freedom for Lebanon" and "Acquittal ... Acquittal ... Geagea, Geagea Acquittal" rang out from the crowd.
A number of political figures have participated in the protest.
Abbas Nasir, Aljazeera's correspondent in Lebanon, said protesters had not received any guarantees from parliament Geagea would be released.
Geagea has been in solitary confinement, spending most of the past 11 years in an underground cell at the Defence Ministry.
He is the only prominent former commander of disbanded Lebanese forces to be jailed for opposing Syrian dominance, while other leaders benefited from an amnesty for crimes committed during the 1975-90 civil war and went on to become lawmakers and cabinet ministers.
At least 2000 protesters called
for the amnesty bill to be passed
Geagea, who led the Christian Lebanese Forces during the civil war, was arrested in April 1994 after the bombing of a church that killed 10 people.
He was acquitted of the bombing but convicted on other charges. He is serving three life sentences for the assassination of political rivals, including the bombing of a military helicopter that killed in 1987 the then-prime minister Rashid Karami.
Geagea's supporters consider him a political prisoner. The human-rights group Amnesty International has called for the release or retrial of Geagea and fellow fighter Jirjis al-Khury. Amnesty said last year that their trial had been unfair. The government denies that.
Geagea's imprisonment and the exile to France of another Christian leader, Michel Aoun, have been open wounds for Lebanon's Christian minority since the end of the civil war.
Past attempts to secure a pardon for Geagea and Aoun's return have been stymied by Syrian influence. But Syrian troops completed their withdrawal from Lebanon last week after intensified international and domestic pressure stemming from the 14 February assassination of former prime minister Rafiq al-Hariri.
Aoun living in exile in France
hopes to return to Lebanon
Aoun's return was expected on Saturday. An aide of his was detained on Tuesday at the airport on returning from Paris.
Fayiz Karam, a former army lieutenant colonel, appeared before a military court, which had sentenced him in absentia in 1992 to 10 years in prison for forming a "group to overthrow the government." He was retried and acquitted within hours.
Later, he told reporters the charges were politically motivated and that he had come to show he was not above the law.
Charges against Aoun were expected to be dropped on Thursday.
An amnesty bill also would free Muslim suspects in jail for several years awaiting trial on state security crimes.
But passing legislation was held up when former prime minister Omar Karami, the late Karami's brother, and the family rejected an amnesty.
Parliamentary elections must begin on 29 May and end on 20 June.
The anti-Syrian opposition, buoyed by the Syrian withdrawal and the fall of some of its Lebanese symbols, hopes to win the voting. But differences over the electoral law have caused divisions within the opposition and the pro-Syrian camps.
The main opposition groups and some pro-Syrian factions favour an electoral law that lays small polling districts.
Others in the pro-Syrian camp favour large electoral districts where they expect to fare better.
But with the 128 parliamentary seats split equally between Christian and Muslim legislators, Christians have complained that their representation will be decided in large districts by Muslim voters.
Parliament Speaker Nabih Berri of the Shia Amal movement, who risks losing seats if smaller districts are demarcated, has been reluctant to call a parliamentary session to discuss a new law before Thursday's deadline to formally call electoral bodies into service.
Berri is reluctant to discuss the
new law in parliament
Lahoud, the Lebanese president, stepped in, sending a letter to Berri to urge the legislature to act, a move that would indirectly call parliament into session. Berri had yet to respond.
The influential Maronite Catholic Church, whose head Cardinal Nasrallah Sfeir is one of the major backers of the opposition, on Wednesday supported small electoral districts, saying it guarantees the best representation of the people.