Normative legal pluralism has to cope with the conflict of the normative claims of competing legal systems. The issue is how to justify legal judgements regarding such conflicts. A methodological device to treat such conflicts is interlegal balancing. Usually, legal statements are justified according to the norms of a particular legal system, according to the criteria of validity established by this system. Interlegal balancing changes the perspective, taking that of law-applying organs, particularly a judge, who faces competing normative claims of diverse legal systems. A specific problem of this approach is the exclusionary character of law. However, regarding law as a normative system, such exclusion cannot hold strictly but must itself be justified, and permit balancing. My thesis is that the arguments relevant for interlegal balancing are those that justify the claims of the respective legal systems. Of special importance are formal principles, which demand compliance with the norms of a system, disregarding their substantive correctness, but because they are established by the respective system. The justification of formal principles refers to arguments why one should obey the law. A systematic approach of such arguments is presented. The conflicting arguments have to be balanced according to the general criteria of correct balancing, that is, according to abstract weight and degree of fulfilment of the competing normative demands.