I think this is the wrong approach, best thing to do is deal with the specific issue, namely the one employee. You say they are a good employee so build on that, discuss the problem and I'm sure that should be the end of the issue.

OR you could show them this post ;\)

Crippling internet access because of one employee doesn't seem to be very effective.

Getting to 2,000 posts; one year at a time vp160/qs8/qs4/SVS 2000/m60/Monolith 3x200 amp