See link: http://www.uscis.gov/files/pressrelease/HandLFinalRule110107.pdf.

Many H and L status holders are confused as to what documents to show upon their return to the United States. This article will help many of H and L nonimmigrants and their dependents understand they could return to their previous H or L status if they still hold a valid visa, meet the admissibility requirements and are gainfully employed with the sponsoring employer.