We had this from a colleague in another thread :
"Wagons of loot and curses of the population" was a rhetorical flourish rather than a legal definition. Having done a fair amount of reading on the revolutionary wars, this is the depressing impression I received. .... I don't have figures, but I don't think the origin of Soult's famous collection of Spanish paintings was disputed"

Sorry, don't know too much about the French Révolution. The discussion here was about the history of the Empire. OK, so we dont have any indications about how much or how often these "wagons of loot" were to be found under the Empire. But it is a useful rhetorical flourish because it demonstrates our distaste for Naploéon ? It is a more refined way of expressing "N. is bad" ? Nothing more ?

OR ....

Maybe we can find a notable individual looter. Not that the alleged thefts of this one man would be enough to effect any economic impact on the scale of nations, but we can at least convey our distaste for the French Empire with an allusion to a single name, some identfible "bad" person who did "bad" things. And so we are given the thief, maréchal Soult.

Could be true. Maybe Soult was a big looter. But I think I will dispute the point, at least a little, by asking to see some evidence for his being a thief. So, let's look into this a little. ....

I found a good amount of accusations of Soult's thefts in the later 1800's, in English, arising after the sale of his art collection in 1853. See, for example:

Artist-biographies‎
Moses Foster Sweetser (1879)

Robert Chambers
The Book of Days (1869)

The New American Cyclopaedia
George Ripley & Charles Anderson Dana (1861)

A Handbook for Travellers in Spain‎
John Murray (1855)

Earlier, and cited in the above, there are accusations of Soult in:

Annals of the Artists of Spain
William Stirling Maxwell (1848)
Here we find such gems as :
"The fortunate collectors who can afford to deal with the Duke of Dalmatia shoud in all cases bargain for pedigrees with their pictures. .... the seller could surely have no objection 'to whisper where he stole' goods which all Europe knows were acquired by rapine".
But, we find little in the way of specific accusation, let alone evidence agianst Soult.

More specific, at least, and a bit more contemporary, is this Spanish work, which seems to be the well-spring of the idea of "Soult as looter":

Historia del levantamiento, guerra y revolución de España
Don José-María Queipo de Llano y Ruiz de Saravia, el conde de Toreno (1786-1843)
Paris: 1832 (and many other editions)
http://www.xtec.es/~jrovira6/bio/queipo.htm
http://www.elmundo.es/suplementos/cronica/2007/612/1184450407.html

A constitutionalist and patriotic nationalist, a representative of the Cortez during the war, writing in Paris without access to archives or records or even witnesses in Spain, his work strikes one today as singualrly polemic and perhaps propagandistic. But, please form your own opinion:

Vol. 1 (1839)
http://books.google.com/books?id=24kPAAAAYAAJ
Vol 2 (1839)
http://books.google.com/books?id=OIoPAAAAYAAJ
Vol. 3 (1839)
http://books.google.com/books?id=iYoPAAAAYAAJ
5 vols bound together (redaction?) (1872)
http://books.google.com/books?id=C1YFAAAAQAAJ

So, other than a few un-sourced accusations, and "what everyone in Europe knows" does anyone have any real evidence of Soult looting artwork ?