我以前研究過24小時說法的來歷，首先這不是法律規定。下載盜版軟體和電影，在1小時內刪除和24小時內刪除沒有區別，都不能作為免責理由。
Is there a 24-hour rule under the copyright law that allows a user to download a program and use it for 24 hours to determine if they want to continue using it - and then after the 24-hour period they have to delete it or buy it?No. The 24-hour rule is an urban legend created and circulated to justify violations of international copyright law on the Internet. Infringement may occur by downloading software, uploading software, making software available for download, and transmitting software files without a valid license to do so. Whenever the distribution of a computer program occurs without the consent of the software manufacturer, it is a direct infringement of international copyright laws. The unauthorized reproduction or distribution of a program, even for only 24 hours, is illegal. The amount of time is not an exempting factor.
出處：ACDSEE Piracy FAQ http:// nl.acdsee.com/support/p iracyfaq
不過我註意到國外律師事務所給網站發函要求刪除侵權連結時（「notice-take down procedure」），一般都要求在24小時內完成；而很多大型網站比如Google也承諾在收到可靠舉報後在24小時內刪除侵權內容。根據美國【數位千禧年版權法】（DMCA）中的「避風港原則」，只要網站在接到權利人的通知後，及時刪除侵權內容，就不用承擔侵權責任。
所以「24小時刪除」的說法可能和通知刪除侵權連結的律師函有關，但和網站不同，盜版軟體和電影的下載者不受「避風港原則」保護，所以24小時內刪除也不能免責。而該免責聲明也沒有法律效力。
