How to join an imperialist war of my colonial nation?

[GaiusJulius]

Hello everyone!
My colonial nation in Louisiana has been attacked by an independent Canada with the Imperialism CB.
Canada dragged its ally France into the war, and they are both dragging my colonial nation through the dirt while I'm watching from the side.
I cannot use enforce peace (it says -1000 invalid target). I have no truce with any of the participants and all the other conditions in the wiki are met.
Does anyone have any idea why this is happening and what I can do to help my beleaguered brethren?

I'm playing Japan, if this is relevant.
Also, it's 1818, so don't worry, I'm not in any hurry for the answer.

 

[flemsh]

The only reason i can think off for the -1000 invalid target is that you are trying to use enforce peace on your cn instead of on Canada.

 

[GaiusJulius]

The only reason i can think off for the -1000 invalid target is that you are trying to use enforce peace on your cn instead of on Canada.

Unfortunately, that is not the case.

I have a feeling that this has something to do with Canada being a former colony of England. Maybe it is somehow still categorized as a colonial nation, and since "Enforce Peace" should draw the parent nation into the conflict and Canada has no parent nation, it appears as an invalid target. i.e I think is is a bug...