Illegal... and also illegal. Seriously, modding Jeeps legally are a PITA. My last Jeep could have been VI'd for any one of over a dozen items and it was a mild build.
| 12 A motor vehicle, except a motorcycle, shall be equipped with a front bumper, and where a replacement bumper has been installed, it shall give substantially the same protection as the bumper originally installed by the manufacturer. |
Obviously a stubby doesn't protect the same area as OEM, thus is illegal.
| 11 The vehicle shall comply with section 19.02 of the regulations with regard to size and dimension. |
Doors—Doors shall be installed in a vehicle where the vehicle was manufactured with doors.
The doors with which a vehicle is equipped shall be in good working order, and any hinge, latch or handle must not be broken, missing or inoperable.
The doors shall not be warped, twisted or weakened to the extent that a slight jar will open them.
A door shall be capable of being opened or closed with normal effort.
This is important as not only are the doors necessary but the mirrors attach to the doors. Many Jeep owners, myself included, have used brackets to remount the mirrors with the doors off or add mirrors that fit in the door brackets. While this adds some semblance of safety and normality to driving without doors, it is not as safe and still illegal. I know someone who wrote off their Jeep because they had their leg leaning partially out of the vehicle and a wasp came flying up his shorts leg and stung him on the inner thigh. That's a worst case scenario but in my experience even small rocks kicked up hurt like hell at speed when you have your leg partially out for ventilation. Anyway, suffice it to say don't be surprised to see anywhere from a ticket to a box 2 for no doors.
edit: I should clarify that pre-86 CJ's like my 67 CJ-5 did not require doors
(and in the case of my 67, even side mirrors) but all YJ's and newer were equipped with doors from the factory and must have doors installed at all times while on the highway.