For the past two and a half years, Lebanese politics was played much like a game of touch football. That is, it operated within the confines of a strictly defined set of rules: It didn't always make for the most compelling sport, but at least nobody got hurt. This was the legacy of the May 2008 Doha Agreement, which gave Lebanon's Hezbollah-led opposition veto power in the new national unity government.

But it's unity no more. The rival coalitions finally faced an issue where no compromise was possible: The Special Tribunal for Lebanon, which was established by the U.N. Security Council to prosecute those behind the 2005 assassination of former Prime Minister Rafik Hariri, is expected to soon issue indictments implicating Hezbollah members in the crime. Prime Minister Saad Hariri, his son, has staunchly resisted Hezbollah's attempts to pressure him to disavow the court. Today, Lebanon's opposition cabinet ministers resigned in protest, forcing the collapse of Hariri's government.

The new rules of Lebanese politics will make for a full-contact contest worthy of the NFL. The parties now begin what promises to be a protracted process to form a new government. The opposition will likely try to pressure Hariri by raising alternative candidates for prime minister. However, any other potential premier would be hard-pressed to help Hezbollah undermine the tribunal's credibility.

"As the son of the slain leader -- with Hezbollah looking for some form of absolution or some way of getting itself off the hook [for the Special Tribunal's indictments] -- Saad Hariri is in a particular position to do that much more so than anyone else," noted Mona Yacoubian, the director of the United States Institute of Peace's Lebanon Working Group.

Few expect the situation to quickly devolve into violence -- the more likely scenario is long-term government paralysis, punctuated by rival political demonstrations organized to show the various factions' popular support. In other words, the country appears poised to return to the political deadlock that existed in 2006, after Shiite cabinet ministers resigned in an earlier attempt to prevent the Lebanese government from lending its support to the international tribunal.

On the bright side, Lebanese political parties are making an effort to prevent the situation from turning into a sectarian turf battle between the Shiite and Sunni communities. Reached for comment, a delegation from Hariri's predominantly Sunni Future Movement declined to comment. A Hezbollah official also said that his party had decided to not make any further statements for the next two days on the matter. By staying above the fray for the time being, the parties are trying to keep this as a dispute between two political blocs, rather than turn it into a dispute between rival sects.

That has left the political field open to Lebanon's Christian parties, which are divided between the two sides. "Any democratic means [to achieve the opposition's goals] are allowed; this is what the opposition has committed to," a senior official of Gen. Michel Aoun's Free Patriotic Movement, the largest Christian party in the opposition, told me. "If there is a need for street protests, why not?"

Labor Minister Boutros Harb, a Hariri loyalist, shot back that "this government will be under the obligation to continue running the current affairs of the ministries" until another cabinet is formed. He also criticized Aoun, saying that his ambition to be president was "a big part of the problem" currently facing the country.

By the standards of Lebanese rhetoric, this is still relatively tame -- Druze leader Walid Jumblatt once referred to Syrian President Bashar al-Assad as an "ape" and a "murderer," but now counts himself among Assad's allies. Lebanon still hasn't returned to that level of vitriol -- but the rules that ensured its politics were kept within certain boundaries have now been broken, and nobody can be quite sure where the game is headed next.