Hi,
I think that Flying_Tuur gave the most correct answer to this question.
JAR 145,which regulates the MEL,says that the MEL is to be used until closing doors,but if a failure occurs after that (during taxi-out i.e)is left to capt.the decision to proceed or not ,using "good sense and good airmanship".
In my point of view,this is a comercial response,since what is good sense to me may not be for you.
There are two reasons to go to MEL:
1.We have to see if we don`t have restrictions to the next leg(out of a maintenance base,etc.)
2.We have to take a look to make sure we donīt have operational restrictions to this flight.
Doesn`t make any sense depart with an item no-go even out of base (unless lamps,emerg.lights,etc.).
When an item is not no-go,normally some restrictions apply like the example given by Flying_Tuur about the pack.My questio is:Am I legally supported if I have an incident above FL250??
But I also agree with LEM...
Companies and countries difer in their rules.Some say nothing about this subject(is left to you),and some use the "moving under it`s own power" rule.
And finally.....don`t forget.....
If you don`t die in an accident ,investigation will kill you.....