Is it illegal to make a left turn and cross over 2 straight yellow lines into a parking lot?

Double yellow only means no passing, left turns are allowed unless its illegal for other reasons. However, it is illegal to turn across a "barrier" or "island" defined by two solid yellow lines separated by a foot or more, with our without signs, optionally colored in with white or black, or with yellow diagonal hash marks. In some places, this rule is amplified by placing physical barriers, such as plastic posts or concrete curbs inside the "barrier" markings.