Star Trek

In "the emporer's new cloak", the Nagus said that universe didn't have cloaking technology.
but in "the looking glass", I just saw a couple of cardassian ships decloak and capture sisko.

I'm sure this has been discussed before, but why would the producers of the show introduce such an obvious gap in this mirror storyline?

also, What is the general speculation on the terrans at this point? Does anyone suppose they ever overthrew the alliance? Was there another terran empire?

Discuss. 

geven time i think that they will.

Furthermore in TOS was too a mirror universe as though in ENT. In DS9 was the Terran Empire overthrown by the Alliance, what the Rebels fought for to regain as a subspecies.

I don't think they would be powerful enough to establish a second Terran Empire, but maybe to continue as a community on the fringes.

As for the thing about the cloaking devices. Yes, it has been mentioned before. It was a mistake on the part of the DS9 writers. Plain and simple.

Yeah, that is a continuity issue. One possible explanation is that the Alliance somehow "lost" its cloaking capability in between episodes, and so had to steal a template from which to make new cloaks. Weak, I know, but it's the best I can think of at the moment.

I like to think of it as the mirror universe counterpart of the "Romulan cloaking devices" error in Enterprise.