If a Magi is residing outside the Tribunals and commits actions that are bad enough to call a march against, then I don't see any issue with that Tribunal voting to march them. After all, who would they complain to?
They are not under the specific jurisdiction of a different (or in fact any) Tribunal which would object to actions taking against them. While being outside of the Tribunal system lets you get away with allot, it also removes a great deal of your protections should some group of Magi be antagonized enough to actually go after you.
Going off my above example, you performed actions against one or more members of a Tribunal which meets the requirements for a march, and they vote to march you. At this point you have very little legally you could do, since you have no valid Tribunal you are a member of that you could turn to as a defense saying "this other Tribunal is attempting to enforce their rules on our Tribunal". You have very little that would actually make the march invalid. If you hear about the march and flee to a different Tribunal, it will not help you any. The new Tribunal will not take up your defense since the actions you performed were outside of their Tribunal against members of a different Tribunal. About your only chance of overturning it is to survive until the next Grand Tribunal, get there safely, and manage to plied your case. Good luck with that though, since news of your March will have spread throughout the order. You are more likely to get nuked by any Flambeau in the area.
I would actually counter that any Tribunal who has members he is attacking could easily target him, since he is not a member of a Tribunal who he could claim protection from.
No Tribunal would want to provide protection to a criminal not of their Tribunal who has taken actions outside of their Tribunal against members of a different Tribunal. Doing so would set a very bad precedent,
If you are not a member of a Tribunal, then code violations you commit are within the jurisdiction of the Tribunal whose members your committed the violations against, by the simple fact that they are the only Tribunal involved.
Yes, but what are the chances that a vagrancy case would be brought against a Magus for not being a member of a Tribunal, if said Magus did not reside in a Tribunal? I would guess unless that Magus had taken some action calling negative attention from a specific Tribunal, not very high. If you do not reside in a Tribunal, then where would the charge of vagrancy be raised? The Grand Tribunal?
If you were a Magus taking part in your Tribunal, would you care enough about the supposed Tribunal Vagrancy of a Magus who did not reside in your Tribunal if they had caused no trouble for your Tribunal to press the charge or vote for it? Consider that it takes time away from more pressing issues.
There are two very important principles in the Guernicus Chapter [HoH]. Firstly a magus must have an official tribunal of residence, or a vacrancy case can be made. The other principle tells us where a case should be heard.
A case is normally heard in the Tribunal where the
actions that led to the charge took place. If the location is
in a border region and the defendant is a resident on one
side, the case should be brought there. If the location is in
a border region and only the prosecutor is a resident of
either, the case should be brought to the prosecutor’s
Tribunal. In all other situations, the case should be
brought to the defendant’s Tribunal.
Possibly disconcertingly, this does not definitely tell us where a vagrancy case should be heard. I suppose though, that vagrancy qualifies as an act, so the case could be heard in any tribunal where the defendant has been vagrating, and furthermore that anything outside existing tribunals is a border region (towards the rest of the world). Or we take the view, which is IIRC taken at least once in canon, that Novgorod covers the rest of the world.
There is another important principle which is easily forgotten. The Oath is not a Penal Code; it is a contract. The central point is that the sodales promise not to cause trouble for each other. If you go so far away that nobody ever hears about the trouble, you have not caused them any trouble, and thus there is no breech of contract. (The famous Flambeau defence of no witness - no crime, is an instance of this reasoning.) If, however, the trouble is so bad that it hits home, then you are in breech, and a case will be made, not because of a subtle legal point but because you cause real damage.
I cannot see anything in canon letting you get off the hook through debate over jurisdictions. You can, however, stay clean by staying out of harms way, literally speaking, of your sodales.
The text in HoH:TL goes on to say that anyone can raise a charge of vagrancy, so I presume a charge of vagrancy due to not belonging to a Tribunal can be raised in any Tribunal.
But you are of course right that if the Magus in question hasn't caused any trouble for a particular Tribunal, then nobody there is likely to care much about his supposed vagrancy.
I think this whole vagrancy issue is a non-issue regarding the OP.
The magus who goes far away has either a portal or another means of transporting themselves to and from the far-away area.
There is thus two locations in play here. One is far away outside of the "jurisdiction" of any tribunal (arguments about exactly what a tribunals jurisdiction means notwithstanding, @loke has some good points on the whole contract deal).
But the other location is sufficiently close to the rest of the order that it is most likely inside a tribunal or inside an area where the members of a tribunal could reasonably pursue a case. It doesnt matter exactly which tribunal, lets assume it is the normandy tribunal.
Consider a case where a magus resident in normandy and with access to a portal to siberia has caused trouble for magi in siberia, where would you bring a case against this magus? Normandy is a reasonable option of last resort.
The teleporting magus could also appeal to any allies in normandy if they were charged/marched/whatever in novgorod.
You cannot answer that question without identifying the Siberian magus. In canon there is no such magus. If there actually is a magus there, he would presumably be a recognised member of Novgorod, and the territory too would be claimed by Novgorod since they have resident members there, so the case ought to be heard in Novgorod by the standard guidelines. If, by strange coincidence, another non-resident magus went to Siberia to be troubled, the case would be heard in Normandy as the defendant's tribunal, assuming that the trouble is actually real and the other magus survived it.
He could, but that is hardly any different from any other case where a magus get into trouble in another (civilised) tribunal. A Norman magus may well get into trouble in Provence, and be marched. The case would be heard where the act took place. He can appeal to allies in Normandy or elsewhere, but any ally helping him would themselves break the code and risk a march on the next Grand Tribunal if not before.
I agree that vagrancy is a non-issue, but it becomes an issue if anyone suggests that a case cannot be heard when the defendant has no tribunal. That is also a non-issue ...
As an aside, by breaking the Oath of Hermes, I was thinking more along the lines of big flashy magic potentially interfering with the local mundane population, and possibly upsetting local faeries.
But everyone elses' interpretations are interesting.
One only has to care about the oath and tribunal if the magi is worried another magi will choose to enforce the rules.
In the modern era, most countries have well developed legal systems with a strong enforcement arm. Even then, wealth and power can deflect that enforcement arm.
In mythic Europe, the full time paid enforcement arm doesn't exist. There's Guernicus and the Quaesitors, however, they are more chief investigator and judge than police.
If someone ignores a tribunal edict, then someone has to hunt them down to enforce it. If the magi is out of the way far enough, any transgression, especially on mundanes in the "non-civilized" areas would have to be spectacular to bring the wrath of the order down.