Prepositions are followed by gerunds. If you have the word such 'in', 'on', 'at', 'with', 'by' and so on, the verb which comes after it is always in the +ing form.

This is because compliance is not a one off action which has been completed. A company (or country) might have to change the way it works to comply with some laws, but the changes need to be permanent and carry on forever and they will therefore be staying in compliance (complying) with the laws continuously..... But this sentence does not make complete sense as it is currently written. It should read: "In complying with trade liberalization laws, the country will expose two key industries, textiles and pharmaceuticals, to fierce competition."