Trade and Commerce
Articles 301 and 303 don't affect existing laws (except as the President may direct by order), and Article 301 doesn't affect pre-1955 laws, or prevent new Parliament/State laws, relating to government trade/business monopolies (the subject referred to in Article 19(6)(ii)).
This specifically protects the government's ability to create and maintain state monopolies in certain trades or businesses (like, historically, railways or certain utilities) from being challenged as violating the general freedom-of-trade guarantee - governments retain the power to reserve certain economic activities entirely to themselves if they choose.
This is part of why the government has historically been able to run certain sectors (like postal services) as an exclusive state monopoly, without that arrangement being successfully challenged as violating the general constitutional freedom of trade under Article 301.