Starting Radicals

If its not in the Rule Book, a Codex, or an official Games Workshop Errata (download off the site), then im pretty certain its not tourny legal. Though im not entirely sure on that one.
Don't rely on what i have to say though, as im usually wrong. Haha. Well i hope im right.

I was under the same impression - things must be printed in a codex/army book, the main rulebook, or in official GW errata to be considered 100% legal and tourney-allowable.

Chapter approved rules from WD are legal in most tournements i think?

i woudn't know. i haven't played in 'official' tournies. i believe it would in fact, be allowed for non epic tournie based systems like in games workshop and what not. however, YOU have to bring in the papers that reveal otherwise. in other words, it'll be up to you to track down that WD and bring that with u to prove those rules. i wouldn't bet on using them for tournies (space marine codex would do a good job negating involvement of relictors with daemon weapons, since people would demand u use traits to customize them accordingly probably..)

As Dorhnkurk said you have to have those papers that have those rules in order to use them. It depends on the tournie organizer whether or not they will allow Chapter Approved rules. Call the organizer before and ask.

Not sure if it's tournament legal but try around WD#288/289 - the article is about using Relictors and their radical Daemonhunter allies.

Hope this helps.