they are trying to sell advertising on my sites, without my knowledge or permission.
Actually, if you are displaying ads from a network, you are pretty much implicitly giving permission for anyone in that network to advertise on your site.
The networks should have some sort of tool to allow you to block certain ads/advertisers. If not, it's time to drop them and go with a different network that has entered the 21st century.
However, the domain registrant who pays the web hosting fees and other website expenses, should be correctly identified by the ad network as he/she/they are the owners of the website, entitled to advertising revenue.
Maybe I'm still missing, but if the ads are showing on your site- you are getting the associated revenue from the network. If the ad network is not paying revenue according to the sites where the ads actually show, then it's definitely time to drop that network!
No direct experience getting a subpoena- your lawyer would handle all that.