First, by now the incident with Parson passing through the portal the first time has probably spread through the magic kingdom sparking rumors already... in a way he is effectively banned from the kingdom, as seen when they rushed him out of the kingdom when he woke up
Maggie rushed him out of the magic kingdom, a fellow GK unit.
Second, the only way other sides will find out is if there are witnesses, and those witness's will agree that Parson looks like a warlord and they CAN'T see his stats
A bunch of unaligned people not talking to each other about a super-wierd thing? Secrets are hard to keep, especially if you got a bunch of people who aren't exactly working together. Especially if some of those witnesses are duty bound to tell their ruler what happened. If they all give different stories, the MK looks even worse and its obvious they are untrustworthy. If they say a warlord (whose stats we can't see) entered the magic kingdom people conclude either, "no way that could happen they are a bunch of liars" or even worse, "the portals are not secure; people could attack our capital using the portals, so we must seal them."
I suspect it will be best for them if they simply say a dangerous looking unit who somehow had his stats vieled entered the MK, and we concluded he was a threat so we croaked him. Also we need to note that they think he is a hippymancer and they don't know what he is planning. The MK casters all
have to decide together that is worth it to risk their neutrality to croak a strange hippymancer. And do this before Parson strolls over to a portal and falls in.
Third, MK will likely give Parson warning before they shoot... if Parson wants to proceed he will have to FORCE his way through; witnesses will be able to see that he WILL NOT listen to reason and comes off as being a threat. As such they would not hold it against the casters for protecting the magic kingdom
First threats are NOT reason. They are the exact oppisite of reason. "Your, honor he wouldn't listen to reason when I threatened to shoot him if he didn't give me all his money, so I really just had to kill him." The MK is neutral gorund. Not controlled territory, its just a bunch of barbarian casters wandering around. Some of which are supporters of GK.
Forth, if there are no witnesses, MK can make up any story they like
Last time there were quite a few. All those random casters with their wands pointed at him? They all have to decide on the same story and NONE of them can talk. No way that happens. Besides, its the freaking transit hub of the MK. No witnesses isn't happening.
Fifth, there ARE guards outside GK's portal... they were placed there ever since Parson came through
Umm... it says this were?
And I was noting the lack of guards on the GK side. Not the MK side. This is important since no guards means that GK thought nothing was coming through the portal. So Jetstone will likely do the same.
A fully armed warlord entering TMK in the middle of a battle with aggressive intent would be considered by every other side to has received what was coming to him if the casters zap him. Parson in armour 'darting' anywhere - seems unlikely.
They think he is a hippymancer and they don't know his intent. So an armed hippymancer (and casters going into battle is SoP for GK) going for a stroll in the MK getting zapped, would seem to me that... the MK just got a little more risky. The only thing even slightly off is Parson carrying weapons. And Parson just needs to go far enough to get into the portal after walking by it; they won't know he is doing anything other than getting advice in the MK until he changes course a foot away from the portal. And that whole promoting himself will help him move just fine. And the casters need to conclude in the second it takes for Parson to walk/dart/trip into the portal that he is a) entering the Jetstone portal b) thats wierd c) he could survive somehow d) its worth the risk to stop him.