On the second floor of the Shababeek cafe, overlooking the clock tower square in the city of Idlib, the side reserved for men was empty except for two young men nursing cups of Turkish coffee. The family side, where women are allowed, was nearly full.

There was no music — just the hiss of an espresso machine and the clinking of cups — and unlike cafes elsewhere in Syria, the air was clear of hookah smoke. That is because of an agreement the owner had to sign with Hayat Tahrir al-Sham, the Islamist group that has ruled for years in much of Idlib Province, in northwestern Syria, and which now controls most of the country with other rebel factions.

“Hookahs and music were banned from the beginning,” said Yahia Naeme, the owner of the cafe, who said the ban had lost him business because many people used to come to his cafe specifically to smoke hookahs. “If we can’t offer it, they’ll get bored and go elsewhere,” he said.

Other cafes in Idlib have skirted the law by offering hookahs in speakeasy-type environments behind closed doors. But Mr. Naeme did not want to risk running afoul of the area’s rulers.