(1) Agreements and arrangements for adjusting prices and production amounts are almost always illegal. During an oil shock, it was illegal to voluntarily decide on as a group the range for price increases and production amount based on administrative guidance issued from the Ministry of International Trade and Industry (MITI) (Supreme Court decision dated February 24, 1984; Keiji Hanrei-shu Vol. 38, No. 4, p. 1,287). Doing so constitutes a price cartel. The base of a free market economy is for prices and quantity to be determined through adjustments between demand and supply as a function of the market mechanism. The conduct of manipulating price and quantity through agreements among companies is almost always illegal, with very few exceptions. Upon receiving administrative guidance from the MITI, it was acceptable for each company to make independent decisions and take self-imposed action. However, a cartel was formed when companies responded excessively to the administrative guidance and formed industry agreements.
A single exception in which an industry agreement was not found to be illegal was the case of a group of bus companies that agreed to take action to reform a situation in which the illegal practice of renting out buses for less than the fees approved by law had become commonplace (JFTC decision dated July 10, 1995; Judgments Vol. 42, p. 3).

(2) Other than agreements which directly affect price, there are also cases in which agreements that suppress price competition or agreements which avoid competition among companies have been found as illegal. There are numerous cases in which it was found to be illegal for medical associations not to display the price for medical service on advertisements, to restrict the number of advertising signs posted, or to establish rules that require approval from nearby hospitals when opening a new medical institution, increasing the number of patient beds, or adding a new medical department (for example, Tokyo High Court; February 16, 2001; Hanrei Jiho No. 1,740, p. 13). Although such rules may have originated from the principle that medical treatment is focused on caring for people rather than pursuing profit, these actions indisputably result in restricted competition for price and quantity. Restricted competition has also been found as illegal in the case of organizations other than medical associations which have put forth plausible reasons for their agreements.

(3) Self-imposed rules are voluntary. As such, each business decides whether or not to participate in said rules. There is a high probability of illegality when forcing a company to participate, when harassing companies that do not participate, or when encouraging business partners to discontinue transactions with non-participating companies. In one example, self-imposed standards for consumer safety were established by a group of toy manufacturers which produced toy guns that fired plastic bullets propelled by the force of compressed air. In this case, it was found illegal for the group to encourage distributors to cease transaction of products manufactured by a company which did not belong to the group and which ignored the self-imposed restrictions (Tokyo District Court; April 9, 1997; Hanrei Times No. 959, p. 115; Hanrei Jiho No. 1,629, p. 70). Although rules may be rational from the perspective of consumer safety, there are cases in which the content or implementation method of those rules is irrational. Forcible participation in self-imposed rules or exclusion of non-complying companies is irrational implementation methods, and thus illegal.