How would that run counter to the law? The law says you can resell it, not how you can resell it.
The law says you can resell it. But Microsoft is setting it up so that only they can resell it, and you get a cut.
This has become common with event tickets in the US, too -- you're free to resell a ticket you've got, but you have to do so via the original issuer via a "transfer this to this other person" function. (Which, frankly, is good for both parties -- you don't need to meet the buyer as the seller, and the buyer knows they're not getting a counterfeit ticket.)
What's best for everyone but the event/venue is if the buyer can confirm that the ticket is valid through a website or phone number, perhaps for a very small fee closely related to the actual costs, before making a purchase.
Hell, it means I'd be able to lend a game to a friend who is across the country. That'd be great, IMO.
The USPS has a thing called media mail. You put the disc in a mailer, and you drop it in the USPS, and it goes very cheaply and in very reasonable time to the other party. Or, in a sane world, you simply either copy to an image and send them the image and they burn to a RW or play directly from the image, or you copy to a RW and send it to them. But since we are living with a bunch of insensible mostly useless copy protection and idiotic laws to support it, you have to be grateful that Microsoft will permit you to lend a game.