• Retailers are again contemplating whether or not to reinstate mask mandates in stores for shoppers and employees, following updated CDC guidelines.
• The National Retail Federation said it is "truly unfortunate" that these mask recommendations have returned for much of the country.
• Apple is asking both vaccinated and unvaccinated customers to wear masks in many of its U.S. stores.
• Other businesses are expected to follow suit with revised masking policies in the coming days.

Retailers have waded back into all-too-familiar territory that they didn't think they'd be faced with again, as many are contemplating whether or not to reinstate mask mandates in stores for shoppers and employees.

On Tuesday, the Centers for Disease Control and Prevention issued a fresh recommendation that calls for wearing face masks again in areas of the country where the Covid-19 virus is spreading the most rapidly. That covers about two-thirds of all counties in the United States. The decision came roughly two months after the CDC in May said vaccinated individuals could go without masks. The delta variant, however, has driven cases back up and led the agency to reevaluate.

The National Retail Federation, a leading trade group for the industry, said in a statement that retailers large and small "will continue to follow the guidance of the CDC."

It added, however, "It is truly unfortunate that mask recommendations have returned when the surest known way to reduce the threat of the virus is widespread vaccination."

Some businesses have been quick to react. On the heels of the CDC's updated guidance, Apple said it is requiring both vaccinated and unvaccinated customers, as well as staff members, to wear masks in many of its U.S. retail stores beginning Thursday. On Wednesday, the state of California, where Apple is headquartered, recommended that all people wear masks indoors regardless of vaccination status.

Disney is also again requiring guests, regardless of vaccination status, to wear face coverings in indoor locations at the Walt Disney World Resort in Florida and the Disneyland Resort in California.

Some have gone a step further and are asking visitors to show proof that they've been inoculated against the coronavirus.

Danny Meyer's Union Square Hospitality Group told CNBC on Thursday that it will now require all guests at its restaurants to show they've been vaccinated. The mandate also applies to current employees and new hires.

"This is the most logical thing I've ever seen," said the founder of Shake Shack and chairman of the fast casual chain's board. "I'm not a scientist, but I know how to read data and what I see is that this is a crisis of people who have not been vaccinated."

Brian Dodge, president of the Retail Industry Leaders Association, is asking that customers be mindful of the new guidance that may be issued in the coming days and weeks by retail establishments.

"As the virus changes, variants spread, and vaccine hesitancy in some populations continues, retailers understand that CDC guidance may evolve and masks may be necessary again in some circumstances," Dodge said in a statement. RILA represents Walmart, Target, Best Buy, Home Depot and other major retail chains.

Spokespeople for Walmart, Target, Best Buy, Kohl's and Nike did not immediately respond to CNBC's requests for comment about any changes to their policies.

A Macy's spokesperson said the department store chain is currently reviewing the revised CDC guidelines.

Joanne Crevoiserat, CEO of Coach and Kate Spade parent Tapestry, told CNBC the retailer is staying close to local guidance and following what local authorities are enforcing.

"We've shown that we can be flexible," Crevoiserat said in a phone interview. "We know how to engage consumers in a masked or remote environment."

Another 'wave of dissent'

Now that many consumers have had a grace period to go mask free, however, confusion and frustration is beginning to ensue.

The latest recommendations from the CDC aren't any easier for companies and customers to follow. The guidelines are tied closely to county rates of Covid transmission, which means a retailer or restaurant operator could have two locations in the same vicinity with totally different policies.

"This leaves a lot of room for discretion and also creates the problem of localized rather than national policies, which can be confusing," said Neil Saunders, managing director of GlobalData Retail.

"Retailers bringing back mask requirements will need to brace themselves for another potential wave of dissent," Saunders added. "There was already conflict around masks and this will only grow as some consumers feel especially resentful that they still need to wear masks after being vaccinated."

Mike Ryan, an employee in the produce department at an Albertsons grocery store in the Rancho Bernardo community in San Diego, said he is anticipating pushback from shoppers in his store.

"It's difficult to walk up and to approach customers ... and push the mandate on them," he said. "It's kind of threatening on their side. But it's also a safety precaution for us as employees."

The United Food and Commercial Workers, the union for 1.3 million food and retail workers, is contending the CDC's latest guidance isn't enough.

"A national mask mandate is the only way we can finally take control of this virus and every retail CEO in the country must recognize that now is the time for all of us to mask up so we can keep our economy open and communities safe," UFCW International President Marc Perrone said.

"With Covid cases continuing to surge, essential workers have been forced to play vaccination police," Perrone added.

Last year, when major corporations such as Costco and Kroger put mask mandates in place, customers didn't always follow the rules. Store workers were often the ones left with the burden of cracking down on unmasked visitors. This time around, that task could be even harder. Especially for fully vaccinated individuals who might feel as if they don't need to don a mask again.

"By having all this flip-flopping, you're creating controversy around the subject, and it opens retailers up to criticism," said Stacey Widlitz, president of SW Retail Advisors. "People get frustrated, and consumers are going to have to wrap their head around it."