Shall we take a look at laws that people talked about trying to pass in the past, in various countries, and then judge those countries and their citizens by this same token? Prima noctum comes to mind..
Oh, for heaven's sake. As noted in the second sentence of the wiki article about Droit de seigneur (the French equivalent of Latin ius primae noctis):

There is no historical evidence that such a right ever existed.

The article goes on to explain that the widespread belief in such a law may have started with the Greek historian Herodotus, who claimed it was an exotic custom of a "barbarian" tribe in Libya. (In other words, Herodotus was quite possibly repeating a "those wacky foreigners" Urban Legend he'd heard secondhand from Greek travelers.) Much later, Voltaire popularized the concept as part of his satires against the ruling classes, and people took Voltaire as gospel.

P.S. In Latin, noctum is the genitive plural form of nox (night). So prima noctum is ungrammatical, but you could say primarum noctum, which equals первых ночей ("of the first nights"). Or, better yet, just say "the alleged right of a king/lord to deflower his subordinates' brides", in plain English.