1-The law will have to work in Pakistan without any Indian involvement.
2-Hafiz Saeed or who ever, is hated in Pakistan, if it is found that he is involved in anti-state activities, he will be punished with the new strict anti-terror laws coming in and the whole nation wanting blood of these rascals. Again, India here doesn't matter. Hafiz Saeed gets convicted, scores double bounty for both Pakistan and India, so that is purely coincidental.
3-Forget Dawood Ibrahim, because there is no extradition treaty b/w the two nations, so even if Pakistan somehow captured him, Pakistan can not extradite him to India.
Now in any case, if Pakistan does want to lend an ear to what India has to say, India would have to offer something.............now what would that be?