H.R. 5323, the "Stop Pot Act," is a bill currently in the 118th Congress to discourage states from legalizing recreational use of marijuana by cutting their federal highway funding by 10%. This is the same method that the federal government used to institute a national drinking age of 21.
The bill would apply to any state "in which the purchase or public possession of marijuana for recreational purposes is lawful." Note that it does not say "lawful under state law"; it simply says "lawful."
Would this actually have any effect, considering that marijuana is prohibited under federal law even where it is not prohibited by state law? Would a state likely succeed in court by arguing that as federal law still applies and supersedes the state's law under the Supremacy Clause, "the purchase or public possession of marijuana for recreational purposes" is not actually lawful in that state (or any other state), and thus the state should still receive full federal highway funding?
I understand that it is highly unlikely that it will pass; I'm asking about how it would be interpreted if it did pass.