Older codes apparently were not clear as to panel location or other restrictions, but the current code is pretty clear on the subject.
2005 NEC section 110.26 defines the required working space in front of a panelboard.
The panel must have a working space width of 30 inches. It can (but is not required to be) centered in the 30 inches, or can be to one side of the other, but must be wholly within the 30 inch working space width. The 30 inch wide working space in front of the panel must be clear from floor to a height of six and one half feet, and the area in front of the panel must be clear outward from the panel for a distance of 36 inches for the full width and height of the working space. Therefore, there should not be any workbenches, washers, dryers, tool boxes or other objects in front of the panel, that intrude on this 30w x 36d x 78h clear working space. This is applicable to all panels, residential, commercial, and industrial.
The panel may be behind an open door, provided the above described working space can be achieved by closing the door. You cannot cover up the panel with a poster or anything else that obscures the panel.
The simple thing to do is shut off the power, remove the panel front, and sand, prime and paint it.
Charles