"They can. It's just that the other owner can easily unmake the portal or put other portals in the area to Ear- to Amenta. Portals can't intersect and unmaking portals that don't interact with one own's dimension is much harder."

"And sometimes walking off the edge of a pocket dimension leaves you in the real dimension, but not reliably?"

Nod. "It can also leave you in another pocket dimension that overlaps the area. It's called vanishing, people reappear on relatively safe places. Surfaces that can support your weight if you can't fly, spaces with breathable air and comfortable temperatures. But that could be on top of a tree or a locked room."

"Or in someone's apartment?"

Nod. "It isn't precise enough that someone could use it to invade an area smaller than... you don't have the same sports... an area smaller than an 300 feet radius. Not without betting on a lot of luck."

"But once it spills over into our neighbors' borders we'll have to have something worked out - it will do that eventually?"

"In practical time frames it doesn't have to. I can expand underground or upwards - I am not sure if that could possibly violate a space treaty or something."

"I don't think so - wouldn't interfere with airspace - one concern is that even if we respect our neighbors' borders it's not clear whether we could prove we're doing so."

"My pocket dimension is spatially fixed. They could send someone to measure it... except that can be faked. ...In theory I could create pocket dimension on both sides of the border and they can keep the other side. Which I would expect to have it's own set of complications."

"All kinds of complications. And the red, if its pocket dimension were permitted to grow that far, would start a war."

"Uh, what? Why?"

"Because reds would have uncontrolled access to their territory with no other way for them to protect themselves and keep their population clean."

"Ah."

"Can you stop the reds from dreamshaping by containing them, or does that not stop it?"

'It does not stop. But I can keep an eye on the pocket dimension."

"Keeping an eye on it doesn't help."

"I am skeptical that the red would want to start a war. What would help?"

"It doesn't matter what the red would want, giving our reds magic that lets them wander freely will cause a catastrophe and letting it extend into neighboring countries will absolutely start a war. There might be a war even if we don't let it get that far, honestly, there'd be a mass panic and then perhaps a coup or Tapa might decide to straighten us out."

"Straighten you out?"

"The fundamental obligation of any government is to maintain the confidence of its citizens that they aren't at risk of pollution everywhere they go. If we failed at that someone who was capable of doing it might conquer us to see that it got done."

"I meant... how would that be done?"

"...they would go to war, and their soldiers would kill ours and then their tanks would roll down our streets and they would arrest and execute our leadership and install leadership capable of preventing reds from dreamshaping and getting out and about polluting everything."

"It was not like it was your fault that the red got dreamshaping. The dimension was not even used to anything besides growing yet."

"Yes, no one will be upset with us about the accident presuming we prevent it from becoming a larger problem."