To save or not to save? Voluntarily Failing Armor Saves

My 6+ Armor Save defeats all incoming attacks!

A thread on the Adeptus Windy City forums recently came up re: players "purposely" failing armor saves in 40K. Several users have come out in support of players "volunteering" to fail a save, whilst some are interpreting the rules as players must make any valid armor saves.

I've played 40K for awhile now, though not so much recently, and I've always felt that both RAW and player etiquette is consistent on this issue - if a player wishes, he/she is not forced to make any armor saves, even for those which may be valid.

The rules for taking an armor save states the following - "Before he removes any casualties, the owning player can test to see whether his troops avoid the damage by making a saving throw." (p. 20)

In this instance, the term 'can' is paramount. This term denotes a choice on the controlling player's part. Whenever a roll or rule is mandatory in RAW, the term 'can' or 'may' is non-existent or the term 'must' is used.

In every other instance of the terms "can/may" coming up in the rulebook, they are considered to be optional and their use is at the discretion of the controlling player. Would anyone say that the following are also mandatory?

Rapid Fire Weapons - p.28

"Models armed with rapid fire weapons can move and fire two shots...models armed with rapid fire weapons may instead fire one shot..."

Consolidation - p.40

"...they may consolidate. This means that they may move D6"..."

IC joining units - p.48

"They can join other indepedent characters...alternatively, an independent character may begin the game already with a unit...an independent character can leave a unit during the Movement phase...

Psychic Powers - p.50

"Psykers can use one psychic power per turn."

Force Weapons -p.50

"The psyker may then take a psychic test to use the weapon's power..."

USRs - p.74-76

May/can are used throughout to denote player choice. Must is used when a rule or roll is mandatory.

In support of the argument that armor saves are mandatory, several users point to subsequent rules which state the term 'must'. For example:

"Roll a D6 for each wound the model has suffered from incoming fire and compare the results to the model's Sv characteristic. If the dice result is equal to or greater Sv value, the wound is stopped." - p. 20

But all these instances are written upon the proposition that the controlling player has already decided to attempt an armor save. As such, they neither make their antecedent rule mandatory nor explain it. Additionally, rules in latter sections again use the terms 'can' & 'may' in relation to taking saving throws, specifically:

"Invulnerable saves are different from armour saves because they may always be taken...even if a wound normally ignores all armour saves, an invulnerable saving throw may still be taken." -p. 20

"...you can carry straight on and roll the saves in one batch....Models struck and wounded in close combat can attempt armour saves...even if the rules for a weapon or attack states that no armour save is allowed, an invulnerable save may be taken..." - p. 39

Even Space Marine armour fails occasionally

Additionally, mandatory rule supporters attempt to argue that the terms 'can' & 'may' grant permission, and this means that the permission is situational (i.e. that is a save cannot be made because of AP, etc., then is it ever not taken"). However, a look at the definitions of rules versus permissions clears this up:

Permission
[per-mish-uhn]
–noun
1. authorization granted to do something; formal consent:

Rule
[rool]
–noun
1. a principle or regulation governing conduct, action, procedure, arrangement, etc.: the rules of chess.

The latter governs procedures, the former grants consent. Permitting someone to do something is different then making them do something. If someone were to tell me "You can buy this miniature.", it doesn't mean I must buy said miniature.

It appears that this issue may be addressed in the INAT FAQ and I can only hope that the council rules in favor of voluntarily failing armor saves.