Actors Kevin Spacey, left, and Michael Kelly appear in a scene from “House of Cards.” (AP Photo/Netflix)

We loved “House of Cards”: the lies, chicanery, double-crosses, duplicity, an occasional murder, sex, drugs and rock n’ roll. Sure. Just a slightly fictionalized version of everyday life here in River City.

But this season they’ve gone just too far. (Spoiler alert!) President Frank Underwood’s nomination of first lady Claire to be ambassador to the United Nations could never have happened. That’s because it’s illegal.

Yes, murder’s generally not legal, either, but our understanding is this nomination is specifically barred by the Postal Revenue and Federal Salary Act of 1967, which is called the Bobby Kennedy law because a section was passed in response to President Kennedy’s appointment of his brother as U.S. attorney general.

The language is both clear and sweeping: It says “a public official …(including the President …) may not appoint, promote [or] advance” a relative in an agency . . . “over which he exercises jurisdiction or control…”

The law defines “relative” as a “father, mother, son, daughter, brother, sister, uncle, aunt, first cousin, nephew, niece, husband, wife, father-in-law, mother-in-law, son-in-law, daughter-in-law, brother-in-law, sister-in-law, stepfather, stepmother, stepson, stepdaughter, stepbrother, stepsister, half brother, or half sister.” (The drafters clearly were unhappy with Bobby Kennedy’s appointment.)

In all fairness, people outside the Beltway probably don’t pay too much attention to these things. So after Bill Clinton was elected president in 1992 there was constant chatter that he would appoint Hillary to a Cabinet, sub-Cabinet or other high position in the Clinton administration. But Clinton couldn’t do that.

And neither could Frank Underwood. (Well, maybe some senators were aware of the law. The Senate rejected Claire’s nomination on a 52-48 vote. But with Underwood when there’s a will … )