I would first disagree with your statement that efforts to enforce such restrictive covenants are sometimes successful. The linked article provides no evidence to support that view. Racially restrictive covenants remain in the public records (as do innocent anachronisms such as an early subdivision named "Swastika Park" named before the Nazi's had co-opted the meaning of this symbol and it was an obscure reference to a South Asian good luck symbol instead), and are sometimes not formally removed from legal documents, but anyone who tries to enforce them almost always swiftly find that doing so is illegal.
Taking a house off the market when a buyer is of a certain race is certainly illegal and has been uncontroversially illegal for decades, although proving a case is often difficult and damages are often hard to quantify.
There are situations where laws that are no longer on the books are given continuing effect, although this particular one is not a good example.
For example, (1) many people think that it is legally required to give a child born out of wedlock the father's surname (it isn't), or (2) think that some or all of the legal disabilities of married women associated with the historic coverture regime in the English common law have continuing effect (almost all of them have been repealed), or (3) give effect in some way or other to historic definitions of libel that no longer have legal effect such as a ban on speaking ill of the dead, or of calling attention to the natural infirmities of someone who is genuinely disabled in an embarrassing manner (truth has been an absolute defense for at least half a century ruling out liability in these cases).
No specific, widely used term to describe these situations comes to mind as I write this answer.