french concept of separation of church and state is strikingly different from that in the us, says jocelynecesari, a french political scientist and research fellow at harvard. >> there is this idea that the state has a responsibility in france to control and regulate religion that otherwise can lead to civil war. >> that control extends to the churches themselves, including notre dame, which all became state property 100 years ago, along with existing synagogues. another example -- in france, for a marriage to be legal it has to take place at a city hall. church weddings are ceremonial but not official, and the wall between church and state doesn't end there. >> in the french case it means also restraining or limiting as muh as possible the public manifestation or expression of religious groups. in other words, in france it's better if you act civilly with no religious affiliation. it's seen as more legitimate, while in america it's quite the opposite. >> but the idea that religion should be kept private has collided with the reality that france has changed. islam is now the country's secon