Comment by j_jochem

The problem is that it is impossible to create an engine that will run on synthetic fuels, but is guaranteed to never run on fossil fuels even if modified / hacked, because they’re chemically identical for all practical purposes. There might be some type of DRM-like solution, but given the economical incentives involved, that will be circumvented by car owners. The whole thing is an incredibly stupid idea and will probably lead to the ICE ban being ineffective.