The article deals with the principle of parliamentary autonomy and the role it plays in decisions of courts carrying out constitutional review. The principles and interests competing with parliamentary autonomy are categorized and analysed against the backdrop of relevant case-law, offering a wide scale of approaches used by courts around the world. Three groups of competing interests are analysed separately: (i) public control of parliaments, (ii) the principle of representation and (iii) the rights of parliamentary opposition and individual members of parliament. Within the analysis, examples of good practice as well as those of unpersuasive approaches are offered. Subsequently, the article offers general doctrinal principles, the observance of which would help ensure that courts do not overreach in regulating parliamentary internal affairs, thus triggering unwanted consequences.