Lawful intercept of VoIP communications

Generally mandated by law and/or regulations to support law enforcement and national security
Is it technically feasible?
Who pays?

Romanidis Evripidis, Lawful Interception and countermeasures: in the era of internet telephony, Masters thesis, KTH Royal Institute of Technology, School of Information and Communication Technology, Stockholm, Sweden, COS/CCS 2008-20, September 2008. https://urn.kb.se/resolve?urn=urn%3Anbn%3Ase%3Akth%3Adiva-91683 Links to an external site.

[slide403] We talked about this already.