First, on the differences: the principle of protecting legitimate expectations means that if people act in reliance on some act of an administrative agency, that reliance should be protected, while the principle of self-binding means that when an agency has repeatedly acted a certain way in a situation and the same situation arises for a third party, the agency must handle it the same way, so the agency itself is bound; the two differ considerably from their basic concepts. Reliance protection arises when a prior measure, trust worthy of protection, causation and the person's action all exist, while self-binding arises when there is a legally comparable situation, the same circumstances, application to the same agency and an administrative precedent, so the requirements also differ clearly. But the two principles also have something in common. Both allow discretion, so when an agency acts against the principle, an unlawful act may come to be recognized as an administrative act at the discretion of the official holding that discretion.

In administrative rules, the doctrine of self-binding matters for discretionary guidelines. Because such guidelines are not binding law, an agency that departs from them does not, in principle, act unlawfully. But if the agency issues a decision contrary to its practice without reasonable grounds, a person harmed by it can argue that it is unlawful for violating the principle of self-binding. One view holds that the administrative rule, combined with self-binding, has turned into binding law, so a contrary decision is unlawful. But the decision is unlawful not because it violated a guideline turned into law but because it violated the principle of self-binding, so that view can be considered wrong.

To add: the General Act on Public Administration, in force since March 2021, writes in the equality principle (Article 9), the principle of protecting legitimate expectations (Article 12) and the doctrine of forfeiture (Article 12(2)). The courts set out five requirements for reliance protection: an official statement of position by the agency, the person's reliance on it without fault, action taken in that reliance, harm to the person's interests from a decision contrary to the statement, and no serious harm to the public interest or third parties. Contrary to the paper, the Supreme Court has also held that an agency is bound by a practice formed under its discretionary guidelines through the equality or reliance principles (Supreme Court decision 2009Du7967, December 24, 2009).