Using your stored CC info to auto-bill you for an unrelated product that you never consented to be billed for is quite likely in violation of their merchant agreement with the CC processor.
Edit: This is pretty clearly not an "error" in the system, so their legal team (if there is one) must consider the billing valid in some way.
Full legal text http://www.fdic.gov/regulations/laws/rules/6500-1350.html
Edit 2: A compliant either though your local attorney general or the FTC may be appropriate. http://www.consumer.ftc.gov/articles/0341-file-complaint-ftc
I doubt they could do that. People are often afraid of such fine print gotcha's but would almost always would not stand up in court.
Contracts are assumed to be "In good faith, and neither for nor against any particular side". Meaning having a clause like 'oh yeah, in addition to your yearly fee of $10, we can also charge you any unlimited amount and you agree to pay'
This would be easily deemed as not in good faith and completely in favor of them (as no sane person would agree to that). Hence judge would throw it out - which may or may not invalidate the entire contract depending on how shady the judge thought they were being.
Their service agreement reads that they have the right to "change part of the Services provided under this Agreement at any time" in section 12. No doubt they're hoping that they'll be able to defend the charge based largely on this.
But there's nothing to support the idea that the "Weblock Program" is a modification of the contracted services (domain registration) instead of a separate program. A couple glaringly obvious problems:
First, the original email stated that the customer "will be protected via our WebLock Program," implying a distinction from the original services. Then there's the subject line, "Your domain is being enrolled in the WebLock Security Program," which is a fairly explicit assertion of the same.
Second, you have the addition of Schedule II to the Service Agreement clearly stating that it's a separate service and not simply a change to the existing ones offered.
In short, they don't really have any magical fine print to even point to (and that's before you start interpreting and responding to them) that can justify this new charge.
But even if they somehow prevailed on the merits of any potential contractual claims, they're still going to get chewed up by their card processor as there isn't a merchant agreement in the world that can justify this behavior.
Impossible for me to believe they are actually doing this. And auto charging the credit card.
Something doesn't add up with this.
Who approved this and were they insane?
The most ludicrous thing about it is that being Network Solutions is basically a license to print money (with industry-leading margins) because of a large legacy customer base who aren't aware or simply don't care that they've been the most expensive, rather than the only game in town for years. So you provoke them into caring? It's like being a casino that steals from your customers. At gunpoint.