After the discussion between Manuela and me, I read these two sources of the "drept regalian" quotation to better unferstand how the atribuțiile de achiziții are derogatory.
https://www.lgdj.fr/droit-administratif-9782275042428.htmlhttps://juridice.ro/essentials/1247/patrimoniul-cultural-si-...I still don't completely understand the author as to how the drept regalian derogates from prior law but, with that caveat, I suggest using Manuela's translation (basically relying on powers pertaining to derogatory procurement procedures) with one revision which unfortunately is not closely supported by the original text.
The problem is a peculiarity of US EN, viz., that almost the only possible meaning of "derogatory" is insulting or slanderous (in the election campaign, the candidate made derogatory statements about their opponent). Therefore, in the legal context, derogatory should be changed to "in derogation of," followed by some prepositional object. It's difficult to choose a prepositional phrase without better understanding the author's (Frier's) thesis, but I suggest "traditional property law," so:
[continued]