The Secret Service is authorized by 18 U.S.C. ยง 3056(a) to protect:[11]
The president, vice president (or the next individual in the order of succession, should the vice presidency be vacant), president-elect and vice president-elect
The ‘immediate families’ of the above individuals
Former presidents and their spouses for their lifetimes, except if the spouse remarries
Children of former presidents under the age of 16
Immediate families, not adult grandchildren
“Immediate families, not adult grandchildren”
And not empty SUVs.