The templars know what Justinia did by the end of Asunder, and the Order is part of the Chantry - the Chantry can't commit an act of aggression against itself. They can't use an escape the Divine, not only approved, but set in motion, to say the mages started the war.
Nothing at the end of Asunder suggests the Templars, in general, know what she has done. Additionally, she did NOT officially approve escape. She helped in secret - calling the Templars to meet with her and sending one agent. She didn't issue a proclamation, nor would I expect her to. She helped them get out, but odds are she didn't officially support the escape and urged them back in public. Just because we know Justinia V is sympathetic to the mages doesn't mean that was an act of the Chantry itself.
Lord Seeker Lambert has "put together" what she has done, and if his note is released to the general Templar Order, they know what she has done but also that she has done it in secret and treachery, not using her office but trickery. I don't know to what degree the Templar Order knows about this, but it certainly was not an order issued down to them from their superiors or the Chantry at large.
The Chantry and the Order are linked, but they are not the same. We see this in DA2, where the Grand Cleric says she cannot interfere with the Circle. Perhaps the Divine has more leeway but only if she uses it in her official capacity, which she does not because she knows she cannot. There is a reason she acts in secret. The Divine can give Seeker Lambert orders, but only orders that fit within his vow. Releasing the mages would not be such an order.
I seriously doubt the general populace or any large group of Templars knew about it immediately. Justinia V lived too long and remained in her position too long for that. I assume there were whispers but uncertainties.
Justinia V, as the Divine, speaks for the Chantry. But if she takes an action in secret, that makes said action not an act of the Divine, and thus it's not an act of which the Chantry approves.
And while Lambert knows what Justinia did, it's highly debatable as to whether or not the Templars as a whole do. The Templars, as an organization, are likely in the dark like the rest of Thedas, and those that left with Lambert did so due to Justinia V's public silence and inaction on the situation, more than anything else. If the Templars as a whole knew what Justinia V did, the whole of Thedas knew what she did... And if the whole of Thedas knew, Justinia V wouldn't have survived 3 days to "broker peace" with the mages, let alone 3 years...
Right, this was not an act of the Chantry. And clearly, the whole of Thedas did not know.
Your right and it is more than that.
The creation of the circles was mutually done by the Chantry, the Mages and the Templars. All sides agreed to what would be involved and expected by each group and the Mages then willing went to the circles.
When the Chantry and the Templars did not live up too their end of the agreement the Mages decided to vote on leaving the circles which they had the right to do. It was then that the Chantry refused to let them go and took up arms against the Mages. It was the Chantry that used forced and tried to imprison or kill the Mages, so the Mages then fought back against the Chantry aggression.
I do not believe the Neverran Accord gave one side the right to disband the Circles, nor do I believe mages were an equal party in the Neverran Accord. They went to the Circles because their other choice was to be hunted, not because the Mages agreed per se. According to every source I can find, the Circles were created between the original Inquisition (which became the Seekers and the Templars) and the Chantry, with the Mages not being given a particular vote or equal share.
http://dragonage.wik...Nevarran_Accord
What Lord Seeker Lambert points out about the Nevarran Accord is that, without it, without the mages in the Circles, under the care of the Templars and the Chantry, there is no reason for the Seekers and the Templars to be united with the Chantry, as their original mission was the persecution of mages and the protection of the people from the powers of magic. They agreed to instead cloister and protect the mages, as well as protect the world from the mages, in the Circles, at the behest of the Chantry, but if their purpose there is forfeit, they will break free and become mage-hunters again. As they were originally formed to do, out of need.
What the mages did by rebelling - and what Justinia V secretly helped them do - was ensure they had no safe place to surrender to. The Nevarran Accord was created to protect mages, while still checking the problem of illegal magic (all magic being illegal at that time and still illegal outside of the Circles that now don't exist). They also made themselves law-breakers, for a mage practicing any kind of magic outside of the guidance of the Circle is illegal.