I think that a warrant that allows the exposure of your IP address through intrusive software that exploits a security weakness is valid, assuming that you receive the software after visiting a site and performing a criminal action. It's suitably narrow, and allows further (appropriate) searching.

The alternative (that I can't say that I mind too much, either) is to prohibit ever catching Tor users no matter what online criminal activities they perform, assuming you can't get their real IP through other means.