No, the regulation includes "400 feet from any structure". So if you fly within 400 feet of an obstacle such as a building, transmission tower, or antenna, you

No, the regulation includes "400 feet from any structure". So if you fly within 400 feet of an obstacle such as a building, transmission tower, or antenna, you are within the law (of the sky). Whether you are within the law of the county or state regarding trespassing is a whole different question.