Is it against the law to be double covered for medical insurance

No... some people choose to have double coverage. Your primary will be billed first and then what doesn't get covered by them will be sent onto the secondary insurance... anything left, you are responsible for. Obviously the down fall is that you are paying two premiums.

My husband has one through his workplace, and I am covered by it. When I had coverage through my workplace, it was secondary to my husband's coverage of me. Between the two, most of the medical bills were covered 100%.