Decriminalization: The Social Justice Approach
The Ideology of Decriminalization
This ideology, like legalization, recognizes prostitution as a part of society. Decriminalization implies the repeal of all prostitution-related criminal law, leaving other criminal laws to deal with the more undesirable parts of prostitution (this is worded poorly – help). Decriminalization aims to treat prostitution like any other occupation, with no added rules or regulations.
However, the aim of decriminalization differs from legalization in its target/emphasis. While legalized regulations are in place to protect the social order and public decency of society, the main emphasis for decriminalization is on the sex worker, on respecting their human rights and agency and improving their health, safety, and working conditions.
A Theoretical Concept
Many feminists argue that laws criminalizing prostitution are part of a wider societal process involving the “social enforcement of repressive norms of feminine sexuality, contributing to the suppression of all active and autonomous expressions of female sexual desire. 
Currently, no countries truly use the decriminalization approach in the way social justice advocates discuss. Therefore, the concept of decriminalization is very much a theoretical ideal advocated by sex workers, social justice warriors, and others.
Like every other career path, any country that legalizes prostitution also regulates prostitution. Just as hairdressers must go through training on zoning regulations, prostitutes in these countries must comply with various building regulations. Yet people advocating for decriminalization argue that there should be no extra regulations for prostitution.
In Summer 2015, Amnesty International voted to support a policy calling for decriminalization of sex work after hearing persuasive emotional arguments from both sides. Amnesty said it decided that decriminalization was the best way to reduce risks for prostitutes. Amnesty International then created a proposed policy on sex work that is now being used to lobby governments with. An excerpt from the policy is below:
"Amnesty International opposes the criminalisation or punishment of activities relating to the buying or selling of consensual sex between adults. This policy is based on the human rights principle that consensual sexual conduct between adults - which excludes acts that involve coercion, deception, threats, or violence - is entitled to protection from state interference (bearing in mind that legitimate restrictions may still be imposed on sex work). This policy is also based on principles of harm reduction: on balance, the available evidence indicates that the criminalisation of sex work is more likely than not to reinforce discrimination against those who engage in these activities, to increase the likelihood that they will be subjected to harrassment and violence (including ill-treatment at the hands of police), and to lead to the denial of due process and the exclusion from public benefits such as health services, housing, education, and immigration status." 
 Hubbard, Phil. 1999. Sex and the City: Geographies of Prostitution in the Urban West. Ashgate Publishers: p. 108
 Amnesty International. 2015. "Proposed Policy on Sex Work."