In this case since it's deed restrictions as part of the land/building sale it's not the government enforcing these restrictions, it's plain old contract law.
The government enforces all contracts, by having the power to impose the consequences of violating contracts. In this case, the government is not doing its anti trust duties resulting in harm to the public.
Perhaps it's just me, but I'm pretty glad that we don't have the government interfering with our every contracted act (a sale is such an act).
On the flip side, without the government to enforce a contract one party has broken, there would be no reason to ever fulfill a contract - you'd have to rely on citizen's force, and history has not shown that it's been particularly good to rely on regular citizens.