The 10th ammendment and overall concept of default rights and limited federal powers is one of the largest obstacles to tyranny, and critically important. The ONLY powers and duties the federal government has are those imposed on it by the people through the constitution, in every other case state rights do indeed trump federal law. In the case of arms, the ONLY power the federal government has is to preserve our rights, and striking down state gun laws as unconstitutional.The only powers delegated to the Feds are written into the Constitution. Other powers are reserved for the States or The People. I must have missed the part about cannibis in COTUS. This would be akin to the reason Roe v Wade was overturned. The only thing about firearms in COTUS says something about “shall not be infringed”. Unless I missed something…
In the case of cannabis, it was pretty much agreed until 1969 the federal government had no authority to do anything other than tax it. Even that was found to be unconstitutional because it was an obvious scheme to ban it, and not a tax for revenue generation in good faith. The CDS and actual ban didn't happen till 1970, and even then the report required to demonstrate cannabis indeed was dangerously addictive with no medical use basically proved the opposite, and that it should not be a scheduled drug at all.
Of course that has been ignored by the government, and till recently a majority of citizens. Billions have been spent in a war against millions of citizens ever since. Between all the schemes, all the court cases finding them unconstitutional, the government's own studies and the lack of constitutional authority in the first place, federal cannabis policy is indeed a case where the federal laws are invalid, and state laws or the right of the people do indeed over-rule it. Or someone can ignore all that for personal reasons, and agree with the totalitarian "ends justify the means" approach of our drug policy. That is the mechanism that has spread to every aspect of lives as the government continues to "discover" crisis after crisis, of course requiring unprecedented powers and funding to enforce policies that have no basis in constitutional authority.