Explain 'freedom of entry-and exit of firms in industry'feature of monopolistic competition

Under monopolistic market, firms are Tree to enter the industry or leave the industry, however new firms have no absolute freedom of entry in industry. Products of some firms may be legally patented. New firms cannot produce those products, e.g. no rival firm can produce or sell a patented item like Woodland shoes.
Still new firms may join any industry if they expect to earn profit. Similarly, a loss making firm may easily leave the industry