What Chevron said was that when the legislative branch gives an agency power to do X and there is some disagreement between the agency and someone else over precisely what X means and the agency's interpretation is reasonable the courts should use the agency's interpretation.
What Chevron said was that when the legislative branch gives an agency power to do X and there is some disagreement between the agency and someone else over precisely what X means and the agency's interpretation is reasonable the courts should use the agency's interpretation.