The problem with using LED is purely in the optics. Nothing exists yet as an aftermarket product that can emulate the cut-off that is present in standard automotive low-beam headlamps. In that sense, it should be illegal to use LEDs, from a certain intensity, to be used as driving lights.

LED DRLs by design are operated at relatively low-intensity. So even if they don't employ a cut-off, it is less likely to cause glare to oncoming drivers. Some cars even lower the intensity when you turn the headlamps. Although, I'm starting to see LED DRLs that blinding, day or night. These too, should be banned, IMO.