The daft rule brought in as part of the latest National Defense Authorisation Act that passed on 22 December will stop getting batteries from CCATL, BYD and four other Chinese firms from October 2027. 

The rule doesn't affect commercial buys by firms like Ford, which is nicking using tech from CATL to make electric-car batteries in Michigan. Tesla also gets some of its battery cells from BYD, which became the new top dog in EVs globally in the fourth quarter. The four other makers whose batteries will be banned are Envision Energy, EVE Energy Co., Gotion High Tech Co. and Hithium Energy Storage Technology Co.

It is unclear why the military should get so frightened about batteries -- it is not as if they can be hacked. The only real concern is that if the US was planning to go to war with China and didn't want its battery powered drones to drop out of the sky.

The decision still needs Pentagon to sort out the details of the new rule. It adds to previous rules in the NDAA that cut off the Defense Department's supply chain from China, including limits on using Chinese semiconductors.

While the Defense Department bans only apply to defense stuff, industries and lawmakers follow the rules as a guide for what things, products and firms to trust in their own business.