Network marketing: is it legal ?

Of late a lot of Indian companies are marketing their products through network marketing or direct marketing. Earlier there were only MNCs who were in this type of business. Many of the people look down on this business because of the pushy and aggressive methods of the networkmarketers.Some are doing very well with their products and some have earned bad reputation.

The question is whether the concept and practices of Network Marketing/Multilevel Marketing or Direct Marketing are legal ?