In the early days of the Arab revolutions, it seemed as if a smartphone might be enough to break the power of repressive governments. These little devices could gather crowds, yes, but even more important, their cameras could document the violence that regimes used to suppress their people.

The smartphone changed the balance of intimidation. The rulers and their henchmen were suddenly at risk of being prosecuted, like Hosni Mubarak in Egypt, or hunted and killed, like Moammar Gadhafi in Libya.

But what about the power of the mob itself, the millions who braved police with little more than those cellphone cameras as protection? What can safeguard the individual against chanting demonstrators in the streets or doctrinaire religious parties in parliament? There is a tyranny of the majority, too.

Here is the next challenge for the citizen movements that are advancing from Tunisia to Syria -- and eventually, surely, to repressive non-Arab states such as Iran and China. Once they have toppled the secret police, the revolutionaries need to draft new constitutions affirming the rights of the individual.

America famously sealed its revolution with a Constitution whose first 10 amendments protected basic freedoms of speech, religion and assembly, and the rule of law. We call them the Bill of Rights, after the 1689 British parliamentary act "declaring the rights and liberties of the subject." That manifesto, in turn, was rooted in the Magna Carta.

A lesson for Arab "founders" is that a constitution is just the beginning. It's not so much the document, as how it's enforced. One model that intrigues Mohamed ElBaradei, one of the godfathers of the Tahrir Square revolution, is the German Constitution of 1949. It embodied what the German people learned from the Third Reich, perhaps history's most disturbing example of a majority trampling individual rights. The document begins with the phrase "Human dignity is inviolable," and enumerates a code to protect that dignity.

"In light of the increasing polarization in Egypt, I believe that, in the new constitution, we need a bill of rights that is inviolable," said ElBaradei, who also cited the Brazilian and South African constitutions. "This is important, to assure every Egyptian that the road to democracy is here to stay."

A useful guidepost for Arab constitutionalists is the chapter on governance in the 2002 Arab Human Development Report. This path-breaking document, sponsored by the U.N. Development Project, with its brave call (in Arabic) for openness, tolerance and responsive government, was one of the starting points for the Arab Spring. The report noted that the Arabic word for "govern" means "to judge," and that a ruler is a "person appointed to judge among people." That resonated with a culture rooted in Islamic jurisprudence.

One line from that 2002 report seems prophetic: "It is no longer possible to delay the establishment of the pluralistic, democratic state in our Arab world."

The Egyptian military recently made a clumsy attempt to manipulate the new constitution to protect the military's special privileges. This blunder brought demonstrators surging back to Tahrir.

On religion, the new Egyptian constitution is likely to maintain an old straddle -- stating that sharia law is "the principal source of legislation," but also offering a broader base for civil society. This language is supported by the Muslim Brotherhood; as with any constitutional provision, the question is how it is interpreted.

Successful constitutions must be living documents. They should list the basic rights of citizens, but they must also specify how these guarantees will be protected. A constitution is meaningless without a court to enforce its promises, and that court, in turn, can be subverted unless citizens are vigilant.

And this brings us back to those smartphones: Today, as never before, citizens have the tools to protect their freedoms. The revolution will be televised, and so will the aftermath.