The Government should alwys begin by impacting those things they can, before they seek to impact their "free" citizens.
For example, Loudoun County should first begin impacting this "light pollution problem" by turning off all street lights. The streetlights are the county's and they can turn them off it they like.
Then they can listen to the important feedback from the citizens and decide whether this light pollution stuff is worth losing their jobs over, or not.
What Loudon County could do is retro-fit their existing streetlights by putting reflectors on them that bounces all the light currently going up from them back down onto the streets. The feedback would generally be how much better lit the streets are.