SAN FRANCISCO  As the proprietor of Chung Chou City, a packed-to-the-gills dried seafood emporium in Chinatown here, Anna Li presides over barrels full of coveted ingredients like dried shrimp eggs and scallops and fried fish stomachs.

The Rolls-Royce of the sea is her shark’s fin, the pricey pièce de résistance of traditional Chinese banquets. “No shark’s fin soup, you’re cheap,” said Mrs. Li, summing up the prevailing ethos toward the steamy glutinous broth, for centuries a symbol of virility, wealth and power.

But in a move that has infuriated Mrs. Li and others in this community, a bill recently introduced in the California Legislature would ban the sale and possession of shark fins, including the serving of shark’s fin soup. Down the rickety alleyways and produce-laden byways of San Francisco’s Chinatown, some see the proposed law as a cultural assault  a sort of Chinese Exclusion Act in a bowl.

Similar to a measure passed in Hawaii, the bill seeks to curtail shark finning, a brutal, bloody practice of the global trade in which the fins are typically hacked off a live shark, leaving it to die slowly as it sinks to the bottom of the sea.