also you may want to look at other options to anacharis..aka brazillian water weed, elodea densa. it is considered a Noxious weed in a whole bunch of States.
Elodea densa, Anacharis densa, Egeria densa are all one and the same. See this:
http://ucce.ucdavis.edu/datastore/detailreport.cfm?usernumber=43&surveynumber=182
Basically, if your LFS sells it, it's not being regulated in your state. The federal government's noxious weed list consists of numerous plants that are common in the aquarium hobby. Unless your state is regulating these materials, the federal government doesn't care about it. This is because not all states have the necessary conditions for a noxious weed to become established. Also, in some states, the noxious weed list arrived too little too late and there are already widespread populations of noxious weeds that are too well-established to ever even consider eliminating them.
This is an excerpt from the federal noxious weed act:
Federal Noxious Weed Act
Sec. 2814. Management of undesirable plants on Federal lands
(d) Exception
A Federal agency is not required under this section to carry out
programs on Federal lands unless similar programs are being
implemented generally on State or private lands in the same area.
I think if a state has no regulations/restrictions on certain plants then it is okay for that plant to be transported into and sold within that state. The federal government, in this case the USDA Plant Protection and Quarantine Division, will not step in and regulate the movement/destruction of plants on their noxious weed list. Basically, if it doesn't pose a threat in a state then they won't bother. It's up to the state to decide if a plant poses a threat......from what I've gathered.
I work with the USDA PPQ division on a joint insect eradication program. I keep meaning to ask for the specifics of their regulations since my LFS's definitely sell plants that are on the list. If I remember to do this, I'll try to get the actual logic behind which plants get regulated and why. But, I'm pretty sure it's because of the exception quoted above.