(Star-Telegram) - California winemakers have now enlisted lawmakers and federal regulators in their latest effort to stop the dilution of some vintage names.

Squeezed by the state’s large congressional delegation, regulators are proposing to restrict further the use of certain crucial words on wine labels. The move would stop out-of-state wine producers from spuriously identifying their wine as coming from a designated California region.

“We’re seeking to maintain the integrity of the name ‘Napa Valley’ on the label,” attorney Richard Mendelson said in an interview.

It’s also about more than just the famed Napa Valley. If successful, supporters say, the regulatory effort will help protect the names of all of California’s wine-making regions, of which there are many.

“I can understand why it would be of concern,” Chris Taranto, communications director for the Paso Robles Wine Country Alliance, said in an interview Friday.

Mendelson represents Napa Valley Vintners, an organization whose 500-plus members maintain a constant vigil over place names. Their past efforts included securing passage of a 2000 California state law requiring that wines labeled with “Napa” or related names contain at least 75 percent Napa County-grown grapes.

The California Supreme Court upheld the labeling law in 2005, rejecting a challenge from the Bronco Wine Company, a large producer based in the state’s less viticulturally prestigious San Joaquin Valley.