These will still need to follow basic rules based on their combat counterparts however they can ignore some of those rules:
Civilian vehicles cannot have any weapons what so ever, they can however fit 2 counter measure blocks.
You can use civilian vehicles to transport other combat vehicles however all of their weaponry must remain offline and cannot be used to defend its transport.
Block limits for civilian ships cannot exceed that of the largest ship class, civilian planes and ground vehicles can still only be small grid and no more than 3500 blocks.
Civilian grids can be used to transport resources from a resource zone provided they do not offer any combat advantage at all.