In (two, I believe) U.S. states, marijuana has been decriminalized. That is, enforcement won't be applied at the state [roughly equivalent to a province] level

In (two, I believe) U.S. states, marijuana has been decriminalized. That is, enforcement won't be applied at the state [roughly equivalent to a province] level. At the Federal [National] level, however, there are still laws that prohibit this. The result of this is that while you can be doing something for which you cannot be charged by the state, the Federal government has the ability to prosecute you at their discretion. This is where the risk comes in; you are at the mercy of the federal government to continue deciding that they won't enforce the federal laws in those states.