The only "stubborn myth" here would appear to be the claim that this is a stubborn myth. Every source you can find on this says it is Massachusetts and 1641 - as far as earliest codification.
The first adjudication in court did occur in Virginia - strangely enough, the first officially declared legal slave owner was himself black.
Actually he was white. A 1640 Virginia court case awarded him a black, runaway, indentured servant service for the man's natural life. The plaintiff's name was Hugh Gwynn. Documented in a January 1898 edition of "Virginia Magazine of History and Biography".