It is legal. and expensive!!! Be carful not to use to much in one spot though. There was a guy standing next to me at the Jr USA this year and he had puss and shit running out of his delt!!! Looked to me like it hurt like hell too! It seems to me that you would want to move it around so the whole muscle gets full. Pointy delts suck in my humble opinion.
if u can get it cheaper go for it.. but be careful of synthol fakes. i know 1st hand that Syntherol Industries has some of the best synthol out right now, its a good clean product, no need to worry about infections.