Ceremonial headdresses are treated together here as a class because they share a single feature: the restriction on who may wear them is not a rule about the object but the meaning of it.
Restriction as content
A headdress marks office, standing or the presence of a being, and it is almost universally restricted. Egyptian crowns marked the kingship, Vajrayana initiations use a five-panelled crown, Yoruba beaded crowns belong to particular lineages of oba, and Sikh, Jewish and Christian traditions all restrict specific head coverings by office. An ordinary person putting one on is not dressing up but claiming something they do not hold, which is why the restriction cannot be waived without emptying the object of what it is for.
The war bonnet, precisely
The Plains war bonnet is the case that arises most often, and it needs stating exactly. It belongs to particular nations of the northern Plains, each feather earned by a specific act, and the right to wear one is conferred rather than assumed. Its use as festival dress and fashion has been objected to formally and repeatedly by those nations, and the bans at music festivals since 2014 followed because they asked. It is not a generic Native American item, most nations never wore one, and its use as though it were is the same pan-ethnic collapse that substitutes a single imagined Indian for hundreds of distinct peoples. This entry describes headdresses as a class and does not detail the making or ceremonial use of any headdress a tradition holds closed.