The first amendment reads: “Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof”; this is actually very different from the current understanding, that no religious exercise is permitted within the government. Congress will not create an established church, like the Church of England, an organization which is favored and to which all believers must belong; nor shall it prohibit religious exercise. So, as much as I dislike Islam, as a religion the headscarf must be permitted. Some Christians wear head coverings and these have always been ignored by federal law (as far as I know). On the other hand, I think the case can be made that Islam is a political system and can be restricted in that area. Also, some religious exercise considered outside the bounds of acceptable social behavior has never been permitted, such as polygamy, underage marriage, or FGM.