CHILE
Recent posts mentioned a non-Chilean getting turned back when trying to leave with a Chilean-plate bike.

PERU
I heard from a guy in the motorcycle biz that the Peruvians block non-nationals from exiting to Bolivia with Peruvian bikes to slow stolen bikes from crossing the border...who knows...maybe Peru just doesn't want tourists draining the national supply of bikes. It doesn't really matter. Peru has started enforcing the law.

ARGENTINA
I have read many times that non-national riders are blocked when attempting to leave AR with a second-hand AR-plate bike.

It's getting harder every year for foreign riders to buy a nicely broken-in bike and rip around South America. =(