No it has not been challenged. If you look at the history of court challenges, they typically require a group with a strong economic interest to fund the challenge. I have been in the anti-WOD movement for 25 years, and I can tell you for sure that there is no-one in this movement with a significant economic interest in ending these laws. George Soros and a few other libertarian millionaires have finally emerged, but they are convinced that the ballot box is the most efficient route to overturn these laws.
One of the problems is the court has a long history of accepting statements made by congress at face value. So laws based on total lies are perfectly constitutional. The CSA is a good example. Nearly every statement in the law is false. So congress has learned how to get around the limits of the constitution, they simply write lies into law and the courts accept them as facts.
In the article you saw before
http://www.freerepublic.com/focus/fr/591110/posts
the Feds do good work at times so you would need to prove your case beyond a reasonable doubt.
The only area I see success in would be the area of law where the Feds can just take private property if it was associated with drug sales or consumption.
An example of this need would be when a person renting your house sells drugs out of the house without knowledge and the Feds take your house even though you knew nothing about any drug sales.
I think that will be modified to require proof before taking rented or borrowed propery. That is how I see it Lloyd.