The 18th century lead urns graced Marcus Dill's seven-bedroom Cotswolds home, Idlicote House, in Shipston-on-Stour, before he sold them for £55,000 at auction in 2009.
Dill didn't realise until six years after he sold them that the urns and their limestone pedestals were listed.
However, Stratford-upon-Avon District Council demanded that he get them back and restore them to the grounds of his home.
The council served Dill with a listed building enforcement notice in 2016, requiring that the urns be put back in their original location. His challenge to that notice has since been rejected by a planning inspector, the High Court and the Court of Appeal.
But, upholding his appeal against that outcome yesterday, five Supreme Court judges ruled that, contrary to what the inspector and the courts had previously decided, the appearance of the items on the statutory list was not conclusive as to their status as "listed buildings".
Lord Carnwath held that in order for something to fulfill the statutory definition of "listed building" there were two essential elements: it must be both a "building" and it must be included in the list.
"If it is not in truth a building at all, there is nothing to say that mere inclusion in the list will make it so", the judge ruled.
The judge ruled that fairness demanded that Dill be permitted to argue that the urns are not buildings within the meaning of the Planning (Listed Building and Conservation Areas) Act 1990 (the Act) and that they should not have been listed in the first place.
Lord Carnwath said: "Since this problem was first drawn to his attention by the local authority in April 2015 he has been attempting to obtain a clear ruling on [whether the urns should have been listed]. On the view I have taken, that opportunity has been wrongly denied to him for five years."
Noting the "disturbing lack of clarity" on the legal definition of a "building", Lord Carnwath gave guidance on the issue.
The judge said that a three-fold test should be applied to deciding whether garden ornaments and other objects are "buildings" in their own right. Regard must be had to their "size, permanence and degree of physical attachment" to the land, he said.
He added: "It is also important to keep in mind the purpose of listed building control, which is to identify and protect buildings of special architectural or historic interest.
"It is not enough that an object may be of special artistic or historic interest in itself; the special interest must be linked to its status as a building.
"That is implicit in the reference to 'architectural' interest. But it is relevant in my view also to the concept of historic interest. The historic interest must be found not merely in the object as such, but in its 'erection' in a particular place."
As to whether the urns were "buildings", the judge acknowledged that there were "arguments both ways".
He added: "On the one hand, it can be said, they comprised a set of elements which had to be assembled together (a 'structure'), required a small crane to move them and to assemble them (as an 'erection'), and were intended to occupy a stable and near permanent position in situ.
"On the other hand, they are not particularly large... it may also be relevant that the vases themselves...are physically separate.
"If they had been resting on the ground, rather than a plinth, I doubt if it would have occurred to anyone that they might qualify as buildings.
"Relevant also is the apparent ease of their installation and removal. These are issues which can only be satisfactorily investigated and determined in the context of a renewed appeal."
The Court sent Dill's case back to the secretary of state for housing, communities and local government for fresh consideration.
He urged the local authority and the secretary of state to give "serious consideration to whether in all the circumstances it is fair to Mr Dill or expedient in the public interest to pursue this particular enforcement process any further".
A statement from law firm Shakespeare Martineau, which acted on behalf of Dill, said the decision may have wider impacts in relation to "applications for removing items from the statutory list".
The firm also said that, if Dill has to face the determination of his appeal, "the appeal inspector would be legally obliged to consider Dill's submission that if these items are not 'buildings' there is no contravention against which to enforce, and in deciding whether they are buildings, to have regard to the criteria approved by the Supreme Court".
Simon Stanion, planning partner at Shakespeare Martineau, said: "This is an important decision not only in terms of the matters that may be raised by way of listed building enforcement appeal, but also in terms of the guidance handed down by the court regarding assessing whether individually listed items, such as the urns in this case are in fact 'buildings'."