My only caution about asking a person (i.e.: cop, state trooper, highway patrol, etc) is you gotta write down the date, their name, badge number, unit they are assigned to, anything you think may help identify them down the road if and when you get stopped for a violation. Just saying, "a cop told me it was okay," won't get you off the hook.
The reason I'm so cynical about this is that I have found law enforcement types are just like the rest of us. Some know the law and what they are talking about, others don't.
-Phil