City Hall has banned snacking near its famous monuments in the historical center. Violators face an $80 fine.
Officials say they want to preserve artistic treasures and decorum in a city that has millions of visitors every year.
The ordinance also bans the homeless from making makeshift beds and takes to task people who loiter in central areas at night, who, "often drunk, not only leave all manner of litter on public grounds and in the fountains, but also disturb the peace."
The ban was passed July 10 and remains into effect until the end of October.
Since the ban went into effect last weekend, police have patrolled sites such as the Spanish Steps, asking tourists to move out and preventing them from sipping their drinks while sitting on the 18th-century stairway that is one of symbols of the city.
They handed out the first fines, too, City Hall said. Corriere della Sera reported that among the first to be fined were three Tunisian men eating and drinking beer on the Spanish Steps.
According to city figures, 7.6 million people visited Rome in the first five months of the year.