1. CISF found large stock of 'tablets' in the luggage. Its safe to assume they were medicines not 'bundles of chemicals'
2. This was a national flight connecting to Aizawl (capital of Mizoram), not international.
3. Uninformed about pseudoephedrine and their use and availability in India, not international law.
4. This is Indian court, not US. Here you get arrested for facebook postings and courts find you guilty.
1) Pure pseudo-eph is not sold in tablet form, only the medicines are, and those med tablets usually contain only milligrams of pseu. CISF isn't stupid.
2) It doesn't matter what flight you are boarding. If you are carrying pseu in pure form in large quantities, you will be arrested, no matter what your destination. The reason is that it is not just trafficking it that is illegal, even possession is. It is not just international people that need to be protected from hard drugs, but Indians too.
3) It is not just international law, but Indian laws also make it illegal to possess pseu. Read the narcotic substances act. (Whether you choose to call it a narcotic or not, it is clearly mentioned in the law that pseu is illegal to possess.) And we won't sign an international law if it contradicts Indian laws.
4) Sometimes that happens. But when it happens, the courts throw away the cases, and the officers who made the arrest end up in trouble. Currently both the officers who arrsetd the girl have been suspended from the force, and pending investigation, they will be disciplined or dismissed or even arrested themselves. Aberrations occur, but by and large, everybody gets a chance to be judged by an independent judiciary. This person will also be given that chance. By the way, the courts DID NOT find the girls guilty of anything. They dismissed the case outright, and the supreme court came down heavily on the police for what they did. The girls are free, the policemen who arrested them aren't. All is well in India.