Space Marines automatically pass Morale tests to regroup, and can take such tests even if the squad has been reduced to less than 50% by casualties, though all other criteria apply. If Space Marines are caught by a sweeping advance, they are not destroyed and will instead continue to fight normally. If this happens, then the unit is subject to the No Retreat! rule in this round of close combat and may therefore lose additional casualties if outnumbered. Usually troops that regroup may not move normally and always count as moving whether they do or not, but these restrictions do not apply to models with this special rule.
Units that include Servitors and Familiars are still subject to this rule as long as the unit contains at least one Space Marine.
Space Marines are still subject to Last Man Standing tests. They will always regroup after each Fall Back move to 'reassess' the situation however.

Profiles:

Unit	Unit Type	WS	BS	S	T	W	I	A	LD	Sv
Chapter Champion	Infantry	5	4	4	4	2	4	2	9	2+

Melee Weapon
Power Weapon: Power weapons ignore Armour Saves, and some may give a Strength bonus or wound on a fixed dice score regardless of the enemy's Toughness characteristic (as detailed in the appropriate army Codex).

Wargear
Terminator Honours:
Purity Seals: If a model with purity seals falls back, roll one extra D6 for its Fall Back distance and then remove one of the dice rolled in order to determine the distance fallen back. If a model with purity seals is part of a unit then this ability applies to the whole unit, not just to the model with the purity seals.