Look at the body language in this advertisement. It contains your answer. The man is busily working/reading/studying at his desk when a beautiful and provocative woman appears with some Hennessey cognac. She is laying down the law as if to say, "Okay, honey. That's enough work tonight. It's time to relax with me now... etc.

This is kind of a weird message to pair with alcohol. Typically laying down the law means taking charge of a situation. Sometimes I have to lay down the law when my kids are misbehaving. My boss will lay down the law if I come in late too often. In the image you're referring to, I suspect that the person is actually a lawyer. It's not using the phrase "laying down the law" in the usual sense but instead is using it in a more literal way to get the reader's attention. That's my best guess anyway.

Not really ... "lay down the law" is a standard phrase meaning to set the rules for others, often in a bossy or aggressive way (that contradicts "civilised".) Here, the other meaning of "lay down" is in play, that of "set aside" ; the suggestion, I think, is that the two characters are lawyers, and are setting aside their work roles over a glass of whiskey. ("Use our alcohol and seduce a colleague" , the picture suggests.) This pulls a third, slang meaning of "lay" into force ; to have sex with. So this is a clever, multi-layered wordplay, with nods to modernity in its use of black protagonists and its suggestion (hint, really) that the woman is also a lawyer and on an equal footing with the man - though that is visually ambiguous - but with a very "old" message of "Buy our product and 'get lucky' with an attractive member of the opposite sex." New and old in one neat, catch-all package ... This gives every appearance of being a straight advertisement ; did Koons really do this, and if so did he do it for money for the advertiser, or did he try to pass it off as art, in some way ...? Ah, OK - it turns out that this is a replica of an ad, painted or printed by Koon's factory team and presented as gallery art, "pissoir" style, Duchamp style. There's commentary at https://www.theartstory.org/artist-koons-jeff-artworks.htm and https://news.artnet.com/art-world/jeff-koons-plays-his-race-card-89892 https://dictionary.cambridge.org/dictionary/english/lay-down-the-law https://dictionary.cambridge.org/dictionary/english/lay-down-something https://en.oxforddictionaries.com/definition/lay https://www.urbandictionary.com/define.php?term=get%20lucky