Console games for emulators are generally distributed as ROM images (or simply "ROMs") on the Internet. Without the permission of the copyright holder or the Entertainment Software Association, this practice is illegal—although few copyright holders appear to care about older games (see abandonware); many copyright holders are defunct; and a few copyright holders have even released their games and demos gratis or even as free software. This illegality is also controversial for long-time gamers and so called old-school gamers. One reason for the popularity of console emulation among fans is due to the belief that many older video games that are no longer on the market are more enjoyable than games currently on the market. Many such gamers argue that the graphical, memory, and hardware limitations of the 8-bit and 16-bit eras forced developers to spend more time on gameplay mechanics. Others have argued that modern 3D graphics have not yet fully matured and that the two-dimensional, sprite-based graphics of older systems encourage a more aesthetically pleasing style.
Another common belief amongst console emulation enthusiasts is that companies can no longer derive income from older titles, thus excusing the distribution of ROM images. This is not always the case with published archived collections, ports of classic games to modern systems, and enhanced remakes provided by the original publisher or copyright holder. Many popular emulation websites have promulgated a myth that a user may keep a ROM image on his or her computer for a period of 24 hours. This idea stems from an obscure provision in copyright law intended to apply to libraries. Many ROM sites similarly claim that it is legal to download the ROMs for backup purposes if one owns a physical copy of the software. It appears that Title 17 USC Section 117(a)(1)  permits making a "space-shifted" copy within the United States using a game copier, but this has never been tested in a court of law. An RPGamer.com editorial argues that console developers (especially Nintendo and Sony) and game publishers may have brought console emulation onto themselves by implementing territorial lockouts or censorship of game content. The legal term for such behavior is copyright misuse.
For more recent systems (e.g., Nintendo's Game Boy Advance and N64, Sega's Dreamcast, and Sony's PlayStation), copyright holders have generally been more proactive about protecting their copyrights, and a number of websites offering ROMs and ISO images have been shut down under threat of legal action.
While most popular ROM files are copies of commercial games, many so-called homebrew programs are created by individuals and small groups and distributed as public domain, free software, or otherwise freely redistributable. These ROMs, often given a "PD" tag in their filenames, are unquestionably legal provided the creators did not infringe on other material in their creation. Even though companies are concerned about games' copyright statuses, some fans argue that they use the ROM images under fair use since some gaming enthusiasts have no intent to sell disks that contain those ROM images.