Usually Certificate is necessary for:
Certification process for products and services might be obligatory or voluntary. Certification system had been created to protect Consumer's rights and avoid import of low quality products. Certification law establish standards and norms which have to be met to receive GOST-R certificate. There are also regulations saying which products are subjects to obligatory certification and which might possess voluntary certificate.
According to the resolution of the State Customs Committee of Russia from 01.10.2000, production of foreign manufacturers imported into FR should meet the national quality standards, therefore is a subject to certification.
Certification GOST refers to specified products or industrial activity of the company. Certificates are issued on a base of expertise results, so products which well went through certification process have no difficulties while registering at customs.
All above information shows why Russian companies and organizations cannot work with products with didn't receive GOST-R certificate.