I am coming back to 40k after taking a long, almost 20 year break. I stopped playing around the time that Imperial Guard Codexes and models were coming out and I want to go back to fielding an Imp army. My question is is the Catachan Codex, published before the newest Imperial Guard Codex valid, especially the rules pertaining to Straken. In the Catachan Codex he costs 130 points but has the Catachan Devils rule, allowing for you to field more than one Devil Unit, counting them as Troops rather than Elites. In the Imp Codex he is 95 points but this rule is not listed. Can I use the Catachan Codex to override the Imp one, spending 130 points to allow me to field an entire Catachane Devil Army? Answers are much appreciated!