Acquisition of biological toxin through the Internet and the mails is fundamentally different than the local use of a similarly proscribed substance, so a statute need not be construed to avoid offending the police power of the states.
Even within such a narrowing construction, acquisition of this substance would be within the plain proscription of the federal statute.
Law implementing international convention is constitutional under the Commerce Clause.
http://www.ca2.uscourts.gov/decisions/isysquery/e893b2c5-2f54-4145-a8ca-90ff73122a40/1/doc/16-819_opn.pdf#xml=http://www.ca2.uscourts.gov/decisions/isysquery/e893b2c5-2f54-4145-a8ca-90ff73122a40/1/hilite/
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.