The resolution, which will go into effect on June 10, comes at a time of increased tensions in Lebanon. Hariri and 22 other people died in a massive bomb blast in February 2005, widely blamed on Syria.
The resolution was adopted by 10 votes to zero with Russia, China, South Africa, Indonesia, and Qatar abstaining.
"By adopting this resolution, the [UN Security] Council has demonstrated its commitment to the principle that there shall be no impunity for political assassinations in Lebanon or elsewhere," U.S. Ambassador to the United Nations Zalmay Khalilzad said after the vote. "Those who killed Rafiq Harriri and so many others will be brought to justice."
British Ambassador to the United Nations Emyr Jones Parry stressed it was not an interference into Lebanon's domestic politics.
"This is not a [impulsive] intervention, interference into the domestic political affairs of a sovereign state," Jones Parry said. "It is a considered response by the [UN Security] Council, properly taken, to a request from the government of Lebanon for action to overcome a continued impasse in Lebanon's internal procedures."
Not everybody agrees with this attitude. Russia's UN Ambassador Vitaly Churkin said the resolution was "an encroachment upon the sovereignty of Lebanon:"
"The plan that has been chosen by its authors is questionable from the perspective of international law," Churkin said. "The agreement between two partners, the United Nations and Lebanon, cannot be implemented if only one side agrees to it."
A UN investigation after the killing implicated Syria and Lebanese security forces in the attack. Syria strongly denies any involvement.
"Those who were behind such a draft resolution should assume the consequences," Syrian Ambassador to the United Nations Bashar Ja'afari told journalists on May 30. "But, definitely, this is something that goes against the interests of the Lebanese people and Lebanon as a whole."
Syrian President Bashar al-Assad has said any Syrian suspects would be tried in Syria and he would not release them to a tribunal.
Now Lebanon has until June 10 to ratify the proposal or the Security Council may independently authorize a tribunal. Pro-Western Lebanese politicians support the move, but it is unlikely the resolution will get unanimous support among all the political elite in Lebanon.