NEW YORK (CNN) - The Massachusetts attorney general's office has reminded seven retailers of a state law against opening their doors on Thanksgiving Day.

Nationwide chains, including Whole Foods (Research),Wal-Mart (Research) and National Wholesale Liquidators, were among those that received either verbal or written warnings to obey the centuries-old law and stay closed, according to the state attorney general's office.

Most of those stores have responded by saying they will not open, according to David Guarino, director of communications for the state attorney general's office. He said Wal-Mart and National Wholesale Liquidators had not responded.

"We have full faith and confidence that the stores will close as they are required to do so by the law," Guarino said. "In most cases, it is just a matter of education, that they just weren't aware of the law or needed to be reminded of it."

Wal-Mart spokeswoman Sharon Weber told CNN that its stores will be closed in Massachusetts on Thanksgiving.

"We would like to be open, but the law is the law and we will respect that," she said.

According to Guarino, the attorney general's office received calls Tuesday from Wal-Mart employees who said the megastore intended to open some stores in Massachusetts on Thanksgiving.

The Whole Foods supermarket chain also came under scrutiny last week when a Massachusetts competitor, Shaw's Supermarkets, wrote a letter to Attorney General Tom Reilly saying Whole Foods intended to violate the old "blue laws," which date from the 1600s.

Blue laws -- named for the color of the paper the first such U.S. laws were printed on -- require all retail establishments to remain closed on Sundays and legal holidays. Most of the laws have been repealed or amended, but stores are still required to stay closed on Thanksgiving and Christmas.

The laws allow retailers with six employees or fewer, such as small convenient stores, gas stations and emergency service stores, including pharmacies, to be open.

"It would be convenient for all of us for stores to be open, but the attorney general believes that this law is there for good reason, to give workers a break on at least one day," Guarino said.

Whole Foods, which was offering its employees double pay to work on Thanksgiving, has since decided to close its Massachusetts stores on Thanksgiving.

The attorney general's office would not comment on the potential consequences for violating the blue laws.

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