Because of the Copyright Term Extension Act of the United States (sometimes called the 'Mickey Mouse Protection Act' because of extensive lobbying by the Disney corporation) and similar legislation within the European Union and other jurisdictions where copyright terms have been extended, works such as the early Mickey Mouse cartoons will remain under copyright until at least 2023. However, some copyright scholars argue that Disney's copyright on the earliest version of the character may be invalid due to ambiguity in the copyright notice for "Steamboat Willie".