Quote: King Street Cat "Wouldn't be hard considering the majority of buying and selling is done online. Could a resale limit be set that only allows resale at retail price plus reasonable seller expenses?'"
Absolutely not, with the single exception of stuff where there is some sort of public interest justification (public order at designated football games, alcohol minimum pricing, and suchlike) the government can't and won't interfere with a free market. It is entirely up to the vendors to self-regulate and could quite easily (but at significant cost) do, but never will. They also mostly have contractual terms that tickets can't be resold but for the most part have zero interest in the bother of enforcing this.
There was the famous instance of
rlViagogo and the RFUrl but I don't think it came to much and certainly had no impact on the vast secondary market for RU tickets