You need something akin to international law to be there. While approximations of that can be said to have existed as early as the Late Bronze Age in Western Asia, and possibly somewhat earlier, I am not aware of an explicit notion of overriding legal, binding, at least loosely codified obligations among states who enjoy something like equal status as such ever emerging before about Renaissance in Western Europe. Without that, declaring "neutrality" is only meaningful in a given diplomatic or military context (which might change) as opposed to a legal one, the latter being what is supposed to be meant by "neutrality" in modern international law as applied to countries like Switzerland. Of course, diplomatic systems had legal structures comparable to international law outside Western Eurasia as well (procedures for war and peace, diplomatic recognition, sometimes semi-permanent embassies, legal frameworks for long range trade, immunities, regulating jurisdiction, layered sovereignties, whatever). But as far as I can tell, legal "neutrality" for a given polity was hard to define in any such structure, unless we are talking about sanctuaries, or otherwise religiously established entities enjoying recognized protection/immunity (more often honored in the breach anyway, ask Delphi).