Neg,

In a word, nothing.

I consider the relationship between the Orcs of the Dearthwood and the City State at this point to be much along the same lines as that of the Saxons and the Franks during Charlemagne's early rule. Sometimes they are at war, sometimes they are at peace. When they are at wr, it is death to step into each other's territory. When they are at peace... it is merely dangerous. But trade occurs. Certainly, no Orc of the Purple Claw will be allowed in willy-nilly. Usually, an Orc will need to leave hostages, plus his weapons, to get into the city. Of course, if the Orc wants to go in incognito, and "dress down" to try to represent himself as an Orc of a different, unrelated tribe, that is also possible.

IMC, Orcs all pretty much look the same from tribe to tribe, though they are broken up into Black, Gray, and White varieties (Strong, Average, Weak, in that order). Most encounters are with Gray Orcs, with leaders being Black Orcs. Goblinoids are another matter, and each Goblin tribe is recognizable by appearance. But Orcs can easily pass themselves off as members of another tribe simply by changing their clothes... few non-Orcs are familiar enough with Orc dialects to know the difference of one accent to another when the Orc is speaking Alryan, too, so that's not a serious problem (though some Dunael Rangers of the Dearthwood can tell the difference...)

The Goblin thing is not official yet, though, so it would not limit your campaign (and shouldn't even if it were "official," as Bob's Rule #1 is "Do with the Wilderlands what you will.")