Graffiti often has a reputation as part of a subculture that rebels against authority, although the considerations of the practitioners often diverge and can relate to a wide range of attitudes. It can express a political practice and can form just one tool in an array of resistance techniques. One early example includes the anarcho-punk band Crass, who conducted a campaign of stenciling anti-war, anarchist, feminist and anti-consumerist messages around the London Underground system during the late 1970s and early 1980s.
The developments of graffiti art which took place in art galleries and colleges as well as "on the street" or "underground", contributed to the resurfacing in the 1990s of a far more overtly politicised art form in the subvertising, culture jamming or tactical media movements. These movements or styles tend to classify the artists by their relationship to their social and economic contexts, since, in most countries, graffiti art remains illegal in many forms.
Contemporary practitioners, accordingly, have varied and often conflicting practices. Some individuals, such as Alexander Brener, have used the medium to politicise other art forms, and have used the prison sentences forced onto them as a means of further protest.
The practices of anonymous groups and individuals also vary widely, and practitioners by no means always agree with each others' practices. Anti-capitalist art group the Space Hijackers, for example, did a piece in 2004 about the contradiction between the capitalistic elements of Banksy and his use of political imagery.
On top of the political aspect of graffiti as a movement, political groups and individuals may also use graffiti as a tool to spread their point of view. This practice, due to its illegality, has generally become favoured by groups excluded from the political mainstream (e.g. far-left or far-right groups) who justify their activity by pointing out that they do not have the money – or sometimes the desire – to buy advertising to get their message across, and that a "ruling class" or "establishment" control the mainstream press, systematically excluding the radical/alternative point of view. This type of graffiti can seem crude; for example fascist supporters often scrawl swastikas and other Nazi images.
Both sides of the conflict in Northern Ireland produce political graffiti. As well as slogans, Northern Irish political graffiti include large wall paintings, referred to as murals. Along with the flying of flags and the painting of kerb stones, the murals serve a territorial purpose. Artists paint them mostly on house gables or on the Peace Lines, high walls that separate different communities. The murals often develop over an extended period and tend to stylisation, with a strong symbolic or iconographic content. Loyalist murals often refer to historical events dating from the war between James II and William III in the late 17th century, whereas Republican murals usually refer to the more recent troubles
