There are specified listed times for legal shooting in every state. If it is before legal shooting hours then it is illegal, period. As far ethics goes that really depends on who you are. If it is in legal hours of hunting and you can positively identify it as a deer and don't trophy hunt I don't see a problem with it. As long as you have tags for both kind of deer. Not everyone cares how big the rack is on a deer.

Now if you were looking for a quality deer to mount and only had a buck tag it wouldn't be a real great idea.

Paul