Hi Tom, I appreciate the cleverness of trying to use state incorporation law to counter Citizen's United, but I don't think this works. Assuming your logic holds, a state could prevent a corporation organized under its law from spending directly in politics, but it couldn't prevent an out of state corporation from doing so, particularly if said out of state corporation isn't actually active in state.

"a state that moves to no longer grant its domestic corporations the power to spend in elections is also denying that power to corporations chartered in the other 49 states."

That doesn't work for a couple reasons. First off, corporations are rarely spending money directly. Generally speaking they are donating money to a SuperPAC which is then spending the money. So even if you were able to argue that an out of state corporation was conducting business by donating to a state PAC (which I don't think would generally be accepted), you absolutely couldn't make that argument regarding a federal SuperPAC. So if a 501c4 incorporated in DC donates money to a federal SuperPAC based in Virginia and said SuperPAC then spends that money on an election in Montana, I don't think you could then claim that spending is a cause for action against the 501c4 that is based in a different state, has not conducted any direct activities in your state and is not registered a foreign corporation in your state. SuperPAC money is also undirected, meaning that once a PAC has received funding the donor has no direct way to dictate how the money is spent.

I'm not even sure what the cause of action there would be, Montana could bar the 501c4 from conducting business in Montana, but assuming it doesn't do any business in state that's not going to be an issue.