palpably unfair act is similar, but i'm pretty sure this is the specific rule in question

"successive or repeated fouls by to prevent a score" is considered to be a form of unsportsmanlike conduct penalized by awarding that score. rule 12 section 3 article 2

rule 12 section 3 article 2

and for the sake of completeness, the introduction to Law 14 specifies that this is a penalty kick rather than a direct free kick 👍🏻

those three crucial words at the end of the above post are defined. Saliba got a yellow card, which means the foul was deemed to be reckless unless there was some other reason he decided to give a card that I didn't see

sure — Law 12 says a direct free kick is awarded if a player strikes or attempts to strike (including head-butt) an opponent in a manner considered by the referee to be careless, reckless or using excessive force