Clannie rules are based on competitive Do Gaming League (DGL) rules that used to be used in MW2.

They are:

Search and Destroy only.

All maps allowed except rust.

Game settings: no of rounds: 12 , swap sides: every 4 rounds. Perks: off. Killstreaks: off. Friendly fire: on. everything else on default for SnD.

Primary Weapons allowed: all Assult Rifles. All Sub-machine guns, Intervention.
Secondary Weapons allowed: Pistols only.

Attachments allowed: Silencer, Fmj, tactical knife (pistols)

Perks: will be disabled

Deathstreaks: Copycat ONLY

Equipment:Flashes, smoke

Lethals: frag only.

Other stuff: If you are just playing for fun then most ppl don't mind if you use Throwing knife instead of frags but in competitive games this is not allowed. The P90 is allowed but frowned upon as it is not a balanced weapon, so try to avoid using it.
Clannie rules try to discourage tactics like camping and knife rushing but as policing these things is impossible, there are no rules against them.

Above all clannie rules is an attempt to make the game as balanced and as skill-focused as possible and eliminate all the noob activities in call of duty that allow you to get kills too easily.