Those who stray are often ostracized by their families and sometimes by the larger community. In one instance Radwan found in his research, a Druze man was going to marry a woman of Shiite and Christian heritage. When the neighbors found out, they visited his parents to express condolences on the loss of their son, as if he had died.
In a case that made headlines four years ago, a Druze woman and Sunni man from northern Lebanon eloped. The bride's family hunted the groom down and cut off his penis.
Some members of the faith are pushing back on the rules.
Walid Jumblatt, head of the Progressive Socialist Party in Lebanon and perhaps the country's most prominent Druze figure, married outside the religion.
On identification documents, the Lebanese government considers anybody with a Druze father to be Druze, even if the mother is not -- a concept that has been embraced among more liberal adherents to the faith.
"Yes, yes, they are Druze," said Hassan Sleem, a Druze resident of Beirut who runs a translation service. "We are a small community. We need more people."
Rima Muakkassa, who lives in Akron, Ohio, where there about 100 Druze families, said that while she never considered marrying outside the religion, her four children could do as they wished.
"In the end, it's not by force. We believe in free will," she said. "The purpose is to enlighten and guide our children so they can make the right choices."
From a practical point of view, the biggest challenge to finding a spouse within the faith is the shortage of other Druze, especially outside the Middle East.
Many second-generation children of the diaspora visit Lebanon or Syria in hopes of finding a husband or wife -- with mixed success.