Why would countries promote protectionist laws, while also negotiate for freer trade internationally?

With the increased globalization, protectionist policies are necessary. Protectionism essentially means the reduction in the volume of foreign trade and putting a cap and check on it.

Free trade refers to import export across the global borders without any severe restrictions.

This primarily benefits local domestic players engaged in export business, as they now have an access to even larger market with increased demand for their products. Thus, they can expand and take benefits of economies of scale and hence earn higher profits. From an economy's point of view, more exports flood the foreign exchange reserves.

Hence, they negotiate for freer international trade.

But, international trade also comprises of cheap imports which might be of better standards and quality, thereby pushing domestic manufacturers and players out of business. To protect them, cut down imports and hence protect forex reserves and promote self reliance, they promote protectionist policies and laws.