It is impossible to transfer into Law after one year. After one year, you will need to apply for the quota for first year Law units, which you then do in second year. If you Pass them both, you can transfer to Law in your third year. Of course, you'd be in a position equivalent to someone in second year Law.
As for Commerce, you can transfer after one semester (half-year) provided you have a GPA of a bit over 2, which is a Pass average. And that should easy.