What economic principles predict that outcome?

I didn't. Can I get the name/quick explanation of the effect?

There is no such effect. As for a basic economic lesson on thinking about this policy: For all the major events that are sold out, many consumers pay more then the face value of the ticket (and sometime much much more). All this "surplus" over face value is money that is divided up between the venue, the artist and ticketmaster. Now this money stays with the consumer. For those shows that are not sold out, you can resell on the secondary marketplace for up to the face value. It removes the incentives for scalpers, and for ticketmaster to manipulate the market.

Id like to understand how this creates a monopoly. It isn't banning the re-sale of tickets, just limits the sale to less than or equal to original cost of ticket.