ATLANTA — Gov. Brian Kemp of Georgia signed a shelter-in-place order on Thursday, shutting down restaurant dining rooms, barbershops, bars and gyms across the state. He called it an effort to buy critical time as Georgia braced for a surge in cases of the coronavirus.

Yet as soon as the order went into effect the next evening, the sandy beaches on Tybee Island, which had been closed for two weeks, were once again open to the public.

The executive order signed by Mr. Kemp, who had been among the governors resisting more-stringent measures, has stirred a backlash from some local officials as it superseded their efforts to curb the virus’s spread, particularly in coastal communities that had moved to close beaches on their own.

“No one wants to walk on the beach more than I,” Shirley Sessions, the mayor of Tybee Island, a community of about 3,000 people just below the South Carolina state line, said in a letter to Mr. Kemp. “However, I firmly believe it is a small sacrifice to pay in the long run to help conquer this Covid-19 enemy.”