Comment The question nobody is asking (Score 1) 79
What does the Constitution say?
Per the Interstate Commerce clause, the Federal government can regulate cross-border transactions. It can require any particular warning labeling that it deems necessary when Roundup is produced in one state and sold in another.
The Constitution does not give the Federal government any type of general 'require warning labels on potentially dangerous products' power. The Tenth Amendment leaves that to the states.
States can require any particular labeling for products sold within their borders. They cannot distinguish between locally-produced Roundup and Roundup imported from another state. They also cannot require that their preferred labeling be used for products sold in any other state.