A question for the legal types

[Andrew]

(This is prompted by the fact that ABCFamily continues to air the 700 club even after Pat Robertson's repeated awfulness, but it's a general question that I'd like to explore.)

If you sell something to me with the proviso that after purchase I can only do "A" with it but never "B", how is that valid once final payment is made? Once it's mine, I have the deed or keys or whatever, how do you have any control over what I do with it?

I know there are specific exemptions for copyrighted content, e.g. books, photos, DVDs, etc. I'm talking general property. If I buy your house and you say "okay, but you can't ever paint the bedroom purple" then what's to stop me painting the bedroom purple once escrow closes and the deal is done? It's not your house anymore, it's mine.

I would love to know how this works, in language suitable for someone who got most of their legal knowledge from LA Law.