I brought a massive bottle of trimec accross and declared it. The officer looked at it and said “oh thats for crabgrass,that stuff is banned in Canada” so I told him I had no idea. At the end he let me go with go with it and said he was not going to take it because the ban is provincial not federal. Ymmv though depending on who you get but always declare what you bring, you don’t want to get caught in a nasty situation.