Should non-genuine products be expelled from markets?

We develop a model in which a `genuine' producer supplying genuine products competes with many `non-genuine' producers supplying the compatible third-party or generic products. We examine whether non-genuine products should be expelled from markets. In particular, we focus on the genuine producer's strategies for driving out non-genuine products: running comparative advertising, building technical barriers, and improving the quality of genuine products. Although the small amount of spending on advertising or building technical barriers improves social welfare, their equilibrium amounts are socially excessive. The quality improvement may raise or reduce welfare, depending on the degree of patent protection. We also find that prohibition of entry of non-genuine producers may improve welfare by discouraging the genuine producer from implementing the drive-out strategies.