Some options that aren't war include: * Make a very public stink about it. Publicize exactly what was done, how and who was involved. Attempt to attract the in

Some options that aren't war include: * Make a very public stink about it. Publicize exactly what was done, how and who was involved. Attempt to attract the interest of the media in the hope that the electorate of the country in question will find spying on allies objectionable. * Raise the issue with the EU parliament or possibly the UN. This may not have hard consequences, but officials having to answer for the behavior of their spy agencies can put pressure on those spy agencies. * Use any of the many cooperative agreements between the countries in question as leverage to demand action against the officials who authorized the spying, evidence that it won't happen again, or compensation. Of course, all of these have potential downsides, and I've ordered them from what I think is low risk to higher risk. The fact that the usual result is a quiet diplomatic protest and sweeping the event under the rug suggests that governments think this kind of spying is acceptable, and the only problem is getting caught.