Not a DOC but maybe a trademark.
The original standards for Meritage seem to have been more strict. The New Wine Lover's Companion 2nd edition 2003 (there's a 3rd edition out) said of Meritage--"it must be the winery's best wine of it's type" and "its production is limited to a maximum 25,000 cases per vintage.
Now it looks like the wine simply must be a blend of at least 2 of the Bordeaux grapes with no single variety making up more than 90%.
http://www.meritagewine.org/faqsWhat do you have to do in order to use Meritage on a wine label?
To obtain a license to use the Meritage name, the wine must be a blend of at least two of the traditional red or white Bordeaux grape varieties. No single variety can make up more than 90% of the blend. Once this criteria is met, you can download a membership application (link) and questionnaire (link) and send it to the address listed on the agreement.
www.phillywinefinder.com