Law of Indonesia is based on a civil law system, intermixed with customary law and the Roman Dutch law. Before the Dutch colonization in the sixteenth century, indigenous kingdoms ruled the archipelago independently with their own custom laws, known as adat. Foreign influences from India, China and Arabia have not only affected the culture, but also weighed in the customary adat laws. Aceh in Sumatra, for instances, observes their own sharia law, while Toraja ethnic group in Sulawesi are still following their animistic customary law.
Dutch presence and subsequent occupation of Indonesia for 350 years has left a legacy of Dutch colonial law, largely in the Indonesia civil code. Following the independence in 1945, Indonesia began to form its own modern Indonesian law, not developing it from scratch, but modifying precepts of existing laws. Dutch legal decisions maintain some authority in Indonesia through application of the concordance principle. The three components of adat, or customary law; Dutch-Roman law; and modern Indonesian law co-exist in the current law of Indonesia.
Indonesia legislation come in different forms. The following official hierarchy of Indonesia legislation (from top to bottom) is enumerated under Law No. 10 Year 2004 on the Formulation of Laws and Regulations:
- 1945 Constitution (Undang-Undang Dasar 1945 or UUD'45)
- Law (Undang-Undang or UU)and Government Regulation in Lieu of Law (Peraturan Pemerintah Pengganti Undang-Undang or Perpu)
- Government Regulation (Peraturan Pemerintah or PP)
- Presidential Regulation (Peraturan Presiden or Perpres)
- Regional Regulation (Peraturan Daerah or Perda)
In practice, there are also Presidential Instruction (Instruksi Presiden or Inpres), Ministerial Decree (Keputusan Menteri or Kepmen) and Circulation Letters (Surat Edaran), which sometimes conflicts with each other.
Once legislative products are promulgated, the State Gazette of the Republic of Indonesia (Lembaran Negara Republik Indonesia) is issued from the State Secretariat. Sometimes Elucidation (Penjelasan) accompanied some legislations in a Supplement of the State Gazette. The Government of Indonesia also produces State Reports (Berita Negara) to publish government and public notices.
The 1945 Constitution is the highest legal authority in Indonesia, of which executive, legislative and judicial branches of government must defer to it. The constitution was written in July and August 1945, when Indonesia was emerging from Japanese control at the end of World War II. It was abrogated by the Federal Constitution of 1949 and the Provisional Constitution of 1950, but restored after the President Sukarno's decree on July 5, 1959. During the 32 years of Suharto's administration, the constitution had never been amended. Suharto refused to countenance any changes to the constitution and the People's Consultative Assembly passed a law in 1985 requiring national referendum for the constitution amendments.
After the Suharto's fall in 1998, the People Consultative Assembly amended the constitution four times in 1999, 2000, 2001 and 2002. Important amendments include the direct presidential election by the people (third amendment) and the presidential office term from unlimited to only two (first amendment), the regulation of which had made the possibility for Suharto's administration held in office for more than five terms. After the last amendment, the People's Representative Council gained more power to control the executive branch, the Regional Representatives Council was established, regional government was recognized in a section and an expanded section about civil rights among other changes. Currently, the constitution consists of 16 sections and 36 articles.
Undang-Undang or simply meaning that Laws can only be established by the People's Representative Council or DPR. The executive branch (the President) can propose a bill (Indonesian: Rancangan Undang-Undang or RUU) to DPR. During the process of establishing a bill into a law, DPR will create a small task group to discuss the bill with the corresponding ministries. When a joined agreement has been reached, then the President shall endorse a bill into law. However, even if the President refuses to endorse a bill that has reached joined agreement, the bill is automatically in thirty days enacted as law and be promulgated as such. When an agreement cannot be reached to enact a bill into law, the bill cannot be proposed again during the current term of the legislative members.
Problems with the system
There are still many problems with the legal system in Indonesia. Many laws and regulations conflict with each other, and because the legal system (including the courts) sometimes does not operate effectively, it can be difficult to resolve these conflicts. In addition, the overall legal system is badly under resourced, both in the public sector and the private sector which provides many services to clients. The Indonesian government and professional lawyers in Indonesia are well-aware of these problems and are working, over time, to improve the system. The rule of law in Indonesia is undermined by rife corruption among the nation's judiciary and law enforcers. 
- 1 MPR is the abbreviation for Majelis Permusyawaratan Rakyat, the official name of People's Consultative Assembly.
- Indonesian Law Reporter (30 June 2009). "Hierarchy of Regulations in Indonesia". Mova. Retrieved 2009-06-30.
- Article 20(1), the 1945 Constitution of Indonesia.
- Article 5(1), the 1945 Constitution of Indonesia.
- Article 20(2), the 1945 Constitution of Indonesia.
- Article 20(4), the 1945 Constitution of Indonesia.
- Article 20(5), the 1945 Constitution of Indonesia.
- Article 20(3), the 1945 Constitution of Indonesia.
- Tony Budidjaja, 'The future of Indonesia's legal profession: A lawyer's perspective', The Jakarta Post, 11 April 2013.
- Josua Gantan, 'Rule of Law Seen as Indonesia's Achilles Heel', The Jakarta Globe, 17 April 2014.
- Indonesian Legal Information — a free information and database of Indonesian laws.
- General Directorate of Laws, Indonesia Ministry of Justice and Human Rights — provides Indonesia bills, the State Gazette, the State Reports, and other government regulations.
- ASEAN Law Association, Indonesia front page