My local convention always puts the legal name on the back of the badge in small font,under the disclaimer statement. If people refuse to allow this-no badge. I believe a local lawyer suggested they do this for the convention's protection. In the times I worked on reg,we had one person refuse to give us his legal name,and he was told no badge. This way,it can't be seen,but is accessible for those who need to know. It is also in the reg records.