Legalities of nursing in the mission field?

I live in Montreal and am registered with the OIIQ. I'm seriously considering going on a Medical Outreach with a US based Christian ministry next spring. It will consist of two weeks of working in a traveling clinic visiting underprivileged locals as well as a couple of refugee camps. It's been a dream of mine for a long, long time.

Does anyone know what the legalities would be for something like that in terms of my license? Is it something that the ministry has to deal with? Do you know if it makes a difference or complicates things if the ministry is from the US?

Thanks
Laura