In case of private parties the arguments against their direct bond by the rules on free movement (especially the danger of excessive transgression of their private autonomy) are strongly prevailing over the arguments for such a direct bond (especially the need of much more effective realization of the internal market's idea). Nevertheless, the values and principles included in fundamental freedoms of the internal market should be in force in case of horizontal relations between private parties as well, namely on the ground of the concept of 'duty of protection' and the concept of 'indirect third party effect' (the latter being the part of the former concept) which were elaborated in some constitutional legal orders of the Member States in regard to fundamental rights. Being bound by the 'duty of protection' Member States are obliged to combat such conducts and acts of private persons which form an obstacle in the free movement. The concept of 'indirect third party effect' obliges the courts of Member States to interpret and to apply of the provisions of the national private law in the light of the fundamental freedoms. Materializing the fundamental freedoms within the relations between private parties the Member States are also obliged to respect the private persons' fundamental rights which are here involved and must therefore thoroughly outweigh fundamental freedoms and fundamental rights in all situations in which this appears to be necessary.