We no longer have an open Legal Discussion forum (we have a closed/archived one here), and since the legality of certain drugs varies depending on location, the only forums that might host that content are the regional forums. If you are not wondering about the legality of the drugs but rather the affects of certain legal highs then that's different.
If you are wondering about some legal cannabinoids then you might find discussion on them in the Cannabis Discussion forum. If you are looking for info on certain RC's then try to do a general search on them by typing the name of the drug into the search hosted by Google, which is location on the top left side of the forum. Some RC's are more regional specific, so you can try searching for them by using the 'Advanced Search' on the top right of the page, then switch the keyword search to 'search titles only' and finally choose the specific forum you want to search in (that option is in the 'additional options' section of the search.
Is there any legal high in particular you are inquiring about? Keep in mind that we don't allow vendor/source discussion of any kind, even if the drugs are legal in your region.