I'm not familiar with the applicable law in Virginia, but you might want to contact the Virginia Coalition of Police & Deputy Sheriffs, which has taken a public stance against polygraphy:

http://www.virginiacops.org/Articles/Polygraph/Polygraph.htm

I'm in Va. Any idea on what the law is?

Unfortunately, the federal law that provides worker protection from the pseudoscience of polygraphy (the Employee Polygraph Protection Act of 1988) provides a categorical exemption to federal, state, and local governments. Thus, the relevant law will be your state's. In my home state of California, peace officers cannot be compelled to submit to lie detector testing. I believe that Illinois has a similar law. But you'll need to check your own state law and any administrative rules that might be applicable. If you are a member of a labor union, you can consult your union representative regarding your rights.

Your assessment that polygraphs are a crock is spot on. For a thorough debunking, see The Lie Behind the Lie Detector.

I work for a L.E. agency and have been accused of an administrative violation. I havent done anything wrong but they tell me that I might have to take a polygraph. I have no doubts about my innocence but I've taken these things before during pre-employment testing and I think that they are a crock. 

Do I have to take it? Is there a federal law that protects me?  Any advice?