Sounds like some states should pass laws protecting yard-sales the same way Montana just did protecting firearms manufacture, sales, and posession. A yard-sale isn’t interstate commerce.
Of course it isn't, but the Wickard Commerce Clause is in effect and SCOTUS may say otherwise:
Where necessary to make a regulation of interstate commerce effective, Congress may regulate even those intrastate activities that do not themselves substantially affect interstate commerce.
J. Scalia concurring, Gonzales v Raich
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Respondents Diane Monson and Angel Raich use marijuana that has never been bought or sold, that has never crossed state lines, and that has had no demonstrable effect on the national market for marijuana. If Congress can regulate this under the Commerce Clause, then it can regulate virtually anything, and the Federal Government is no longer one of limited and enumerated powers.
J. Thomas dissenting, Gonzales v Raich