"SN is not really illegal substance." , this makes no sense. The substance is rather banned or allowed.
Don't overthink it. You just have to answer some questions:
- Is the resource banned in the airport or the specific aircraft, company you are flying with?
- Is the resource banned in the country you are in?
- Is the resource banned in the country you are moving to?
I think you can find all the answers on the internet, either by entering the name of the substance or the chemical code or the CAS number.