I mean as the law of the land. Dred Scot unsuccessfully appealed to the rule explicated by Lord Mansfield that any slave brought to the free soil of England could claim his freedom as a subject of the King.
It was the law of the land and permitted long after the Colonies were established. Wilberforce challenged the laws by demonstrating that they were legal persons and met the same requirements as everyone else.
I can bring up his arguments in Parliament. They are the same ones advanced by the abolitionists in the States. Again - the difference there is compensation - they negotiated beforehand as many prominent slave owners sat in parliament.