Wilsons Sandbox

I have been thinking about getting a Laser Pro-Duro because my stock exhaust has developed the dreaded "tweet" and because the Pro-Duro seemed to have the fewest problems (based on my reading of posts to the list). I am wondering, however, if the lack of USFS approval is a problem, I have just moved to a place where I can ride on BLM land. Is the Pro-Duro unable to pass USFS standards or did the maker just not get it approved? What kind of trouble would you get in for riding on government land without having the sticker on your exhaust? Thanks, Tom A-14