I'm suspicious. Nowhere in that article is anyone in the field or in law actually making the accusation of illegality. It seems to be the CNet guy's specul^H^H^H^H^H^Hinvestigative reporting.
Also, there seems to be an affirmative defense, and I don't know why EFF doesn't mention it, except to avoid offering legal advice without a retainer (and thus being useful) or maybe just avoiding US-specific advice:
The packet is encrypted with the exit node's public key. Since they are the only people on the planet that can read the packet, that makes them, by definition, a party to the communication.
A probably totally irrelevant point is that Washington is a two-party consent state, but I'm not aware of any precedents to extend that to non-ephemeral communications like packets.