No, what I said doesn't mean we abolish all State laws - it means that there are concurrent Federal and State jurisdictions on certain matters and that even if a State no longer has a legal penalty for some act, as long as it is a matter of at least concurrent Federal jurisdiction, then the Federal laws can be enforced - with or without any State action and not just on Federal property. The income tax analogy fits very well - even if your State has no income tax the Federal tax is still collected. Likewise, even if your State has no law on a specific subject (like drug possession) IF there is a valid Federal law then it can be enforced anywhere.
I guess it's a good thing I said it was legal on the State level and not the federal level.