ideas are not illegal

a) Idea/idein - "to see"...nature sets apart what one sees aka moving differences (perceivable inspiration). Few suggest idealism to tempt many to consent to concepts/archetypes/things formed together/-isms etc. aka to suggested information.

One such ideal-ism is "not" aka nihil-ism (Latin nihilo; nothing)...

b) As for illegal... https://www.etymonline.com/word/il-#etymonline_v_34622

Il-legal implies being within natural law as crime/krei - "to sieve" aka to separate the finer from the coarser parts of disintegrated matter, which is what natural L(and) A(ir) W(ater) does to any particle of matter living within.

A gentile implies a "crime within law", which is why a jew suggests the inversion...follow laws and punish crimes.

Legal vs illegal implies a gentiles mind within natural law (il-legal) ignoring natural law (legal), while fighting other gentiles, within conflicts of reason, about which jewish suggestion is legal vs illegal.