[solved]prevent netherportal at spawn

Maybe check the range of your spawn localisation and check on blockplaceevent if obsidian is used then cancel it ?

Just an idea

 

I believe there's a portal create event. Will look into it when I get home.

 

I've just done a plugin for you, it prevent the nether-portal in the nether or in another world you set in the config, it's so simple, if you need to prevent the creation of portals in more than one world i can modify my plugin to do this