[quote=@The Lioness]
[@Andreyich] technically a inquisitor could exterminatus a shrine world if he felt the need and not have to get permission from the ecclisiarchy. Inquisitors really answer only to themselves
[/quote]
Yeah, then be excommunicated and killed by his Brother Inquisitors, or simply the Sororitas.

[quote=@NecroKnight]
[@Andreyich]

[u][i][b]I)[/b][/i][/u] You have a single civilian with a gun. Whom can't authorize any connection to the Ecclessiarchy - else its BLAM to the nearest Priest who allowed it. Since Men under Arms is HERESY!

[u][i][b]II)[/b][/i][/u] The Ordo Hereticus has been charged with watching over the Ecclessiarchy - and they can easily BLAM or EXTERMINATUS any planet they wish. Look at the War of Disbelief, if you don't believe it.

[u][i][b]III)[/b][/i][/u] And look at the Imperium as a whole. Do you think, any trigger happy civilian would be wagered over a Imperial Guardsman? As easily as some Priest can make-up a story - said IGs can easily make-up a story of you spouting HERESY and a Commisar BLAMing you for it.

[u][i][b]IV)[/b][/i][/u] And then its a Commisar + the IGs + all their arnaments vs your priest with his chainsword. I am wagering of the Imperial Guardsmen here - since they aren't the Emperor' Hammer for nothing.
[/quote]

1) the Priest can still defend the man.

2) Well it has not been invoked, has it? Yup, it has not. 

3) no but the Frateris Militia has it's own military grade gear and sometimes even has ancestral archaeotech because random people dig up family heirlooms and such for it. Plus, lower Priests and Preachers are generally held above even Lord Commissars in some cases. 

4) It's not a one man army, there is a fuckton of more Frateris Militia members. She pulled the gun on me, I'm getting people to screw off, I've got the plausible deniability here.