There have been several attempts, mostly by big US software companies, to enforce patents and copyright on user interfaces. Such legal action aims to restrict the use of certain command languages or graphical user interfaces to products from one software supplier. This is undesirable because it either forces users to buy software from the company whose interface they have learned or to learn more than one interface. An analogy is often drawn with the user interface of a car - the arrangement of pedals and steering wheel etc. If each car manufacturer was forced to use a different interface this would be very bad for car users.

Following a non-jury trial, which began in early January 1987, a federal judge ruled on 28 June 1990 that keyboard commands and on-screen images produced by Lotus Development Corporation's popular 1-2-3 spreadsheet are protected by copyright. Paperback Software International and subcontractor Stephenson Software Ltd. who lost the case, argued that the copyright applies only to the inner workings of the software. US District Judge Robert Keeton wrote that "The user interface of 1-2-3 is its most unique element and is the aspect that has made 1-2-3 so popular. That defendants went to such trouble to copy that element is a testament to its substantiality". Defence attorneys had argued that the Lotus commands represented "instructions for a machine rather than the expression of an idea".

Soon after this decision, on 2 July 2 1990, Lotus sued Borland International and the Santa Cruz Operation for producing spreadsheets (Quattro, Quattro Pro and SCO Professional) whose interfaces could be configured to look like 1-2-3's.