Eh. One of the best things about Fallout is the fact you almost never are put in a situation you can't get out of with your set of skills; There's usually a solution that just about anyone could approach, though some are simpler, and perhaps more profitable than others. You could convince someone to look the other way as you go into somewhere restricted, or you could bribe them using either money or something else they'd want. Could be as simple as swiping his key, and then slipping inside during an opening in the guard's shifts to do as you please. This one would require carefully sneaking out, and not alerting anyone while you were inside, though. 

There's other options that could be made open, too. Using a distraction and knocking out the guard to get the key instead, or if your character is ballsy enough, just kill him! But make it quiet, or a scene will break out. Then you'd be screwed, probably, lol.