Sure why not? the incident commander gave you a direct order, which would render the scene unsafe. best to pack up your toys and go home, especially if following the order would substantially and unnecessarily increase the danger level of the scene . if there are any negative outcomes, it falls on the person who gave the order, as he is in charge. And for the record, I have never heard that a cop needs to consult with anyone before making a LEO decision, and traffic control and accident investigation is a LEO decision (legally, operationally is a different story).
Taking it to the extreme, yes, leave the patient on the roadway. why? because XYZ CHP trooper ordered us to, and he was in charge of the scene, and legally it's his decision. Don't like it? have the legislative body pass a law saying that Fire or EMS is legally in charge of every MVA, and LEO need to follow their direction.
Lets take this to the extreme: thoughtout the US, LEOs (particularly state troopers for some reason) has a well documented history of arresting firefighters for failing to follow their directions.
Legally, the LEO is in charge of the scene. If your supervisor were to give you a direct order, and he is legally in charge of you, why should you not follow it? after all, if anything bad come from it, he was the one who gave you the direct order, and he is (overall) responsible for everything that happens, both good and bad, on the scene.
We (fire and ems) fight these battles all the time,
https://www.statter911.com/2014/08/...ne-arrested-failing-obey-sheriff-crash-scene/
http://articles.sun-sentinel.com/1993-01-04/news/9301010633_1_clark-accident-fire-rescue
https://www.statter911.com/2016/12/...sted-for-shoving-cop-who-vented-burning-home/ (ok, this might have been justified legally, but still a poor decision by the cop)
http://www.fourwinds10.com/siterun_data/health/safety/news.php?q=1203383265
https://www.firerescue1.com/inciden...for-apparatus-placement-awarded-17-500-in-Mo/
http://www.theblaze.com/news/2014/0...ds-up-handcuffed-in-the-back-of-a-police-car/
https://www.statter911.com/2014/02/...r-brother-arrested-traffic-control-spat-cops/
and a new clip with video of what happened in California
most of the time, the courts side with who had legal authority to be in charge of the scene, and whether or not the LEO had the legal authority to give a lawful order (but not always, it all depends on state law).