Can a wallet deny payments to it? Once my public wallet address is known, is there anyway to deny payments to that wallet?

For example, if I want an external authority to regulate who can pay into a wallet, is that possible?  

I guess a related question is can I turn a wallet 'off' once it is in the block chain and known.
No, you can't prevent people from paying any particular address even if you control that address.  This is a known problem: it would be very nice to have an address that can only be paid once.

Something like P2SH^2 could help with this, although it would not provide a perfect one-time-only property.