This is very handy for doing an end-run around constitutional issues. If each country is not allowed to spy on its own citizens, but is free to spy with impunit

This is very handy for doing an end-run around constitutional issues. If each country is not allowed to spy on its own citizens, but is free to spy with impunity on others, all you need is a strategic alliance (Canada <-> USA) where each country spies on the other's citizens and passes along information of interest.