South Dakota Codified Laws
Chapter 20B - Bicycle Regulation
Section 32-20B-14 - Helmet requirement for Class III electric bicycle.

32-20B-14. Helmet requirement for Class III electric bicycle.
Any person who is less than eighteen years of age and operating a Class III electric bicycle and any person who is a passenger on a Class III electric bicycle, regardless of age, shall wear a properly fitted and fastened bicycle helmet.

Source: SL 2019, ch 135, ยง6.