Although you should ask your bishop first as the canon law directs, since the alb is the vesture of all Christians, it certainly does not mean that one is trying to be part of the clergy, as all the faithful have the right to and could wear an alb to church. I believe it is usually much more fitting for someone leading public offices to be vested than wearing regular street clothes, for some of the same reasons that the clergy wear them. Of course, other vestments such as stole and chasuble should not be used by lay people.