Yes they can. They are very easy to loosen one handed, just by pulling on the toggle pull tag. Tightening is more tricky and we have developed the Greeper Assist specifically to allow one handed people to be able to use Greeper Laces with ease.
Greeper Assist
https://www.wix.app/stores/02b0b5b5-7b9e-48e8-a638-4bd106defd81/catalog/7fa1fdc9-0a30-84c5-093e-5b80a9930add?d=https://www.greeper.com/product-page/greeper-assist
