For Scotland to be a member of NATO they would have to agree to the nuclear sharing policy. That is is a concept in
NATO's policy of nuclear deterrence, which involves member countries without nuclear weapons of their own in the
planning for the use of nuclear weapons by NATO, and in particular provides for the armed forces of these countries
to be involved in delivering these weapons in the event of their use. This would go against the nuclear free
Scotland that the SNP has stated it wants.
As for membership of the EU, membership of a new country has to be agreed to by all existing members. Several
EU countries have their own separatist and/or independence problems - Catalan separatists, as well as pro-independence
Basques in northern Spain; Corsicans who want to break away from France; and Flemish speakers in Belgium demanding
more autonomy, independence or union with the Netherlands. For those countries to agree to an independent Scotland
joining the EU would surely be a green light for trouble at home.