It's illegal to wear a military uniform without a good reason (you're a soldier, a veteran, or you're playing one on TV)... police would be state law, but most places probably have laws against impersonating an officer of the peace, or something like that.
The disguise game is pretty underwhelming at the moment. I played some Decker roguelike recently, and I really liked the way occasionally programs would question you, and you'd have to make a bluff check to prevent them from throwing an alarm. If you pass the check, they leave you alone no matter what you do, short of violence or other major disruptions -- they assume you're supposed to be there. If you fail the check, you might get a second chance (assuming you don't fail horribly), but even if you pass it, the entire system will be on yellow alert.
Perhaps instead of just looking at you suspiciously, most characters will always ignore you if you're in disguise. Security guards, police, and archconservatives might question you; if you bluff successfully (which is a disguise roll against their wisdom), they're happy and ignore you. If you fail, the site goes to "conservatives suspicious", and they continue to question you. A failure at "conservatives suspicious" sets off the alarm. Evading when someone is questioning you counts as one failure... so if a Hangin' Judge starts questioning you as you tromp around the courthouse in your expensive suit, you can just walk past and pretend you didn't hear him. But you can only do that once. A second time ignoring someone, and the site will alert...
Without a disguise, anyone can question you, and you are at a significant bluff penalty. Police uniforms and death squad uniforms (if death squads are active) could be used out of place, and negate the disguise penalty, but not the ability of anyone to question you (your dialog responses would be very "Bavarian Fire Drill"). Bluffing while robbing apartments would involve a disguise penalty.