It isn't meant for tourists bring in a ziploc bag with their liquids in it. Or even the average Joe in Kenya who happens to have a plastic bag or two. It is targetting those who manufacture or import plastic bags.

https://www.nytimes.com/2017/08/28/w...-bags-ban.html
"....Judy Wakhungu, Kenya’s environment minister, tried to allay people’s fears, telling Reuters that the ban was primarily aimed at manufacturers and suppliers. “Ordinary wananchi will not be harmed,” she said, using a Kiswahili word for “common person.”..

...The new regulations call for a fine of $19,000 to $38,000 or a four-year jail term for those manufacturing or importing plastic bags in Kenya. Plastics used in primary industrial packaging are exempt, according to the National Environment Management Authority, although it said that the new regulation would prohibit retailers from selling garbage bags".