Is it legal for a prospective employer to demand a headshot along with a resume?

I’m not talking about entertainment-based jobs.

I search the job ads on Craigslist daily, and I’m shocked at the number of ads that ask for a photo to be sumbitted with a resume and cover letter.

This one for a medical receptionist, for example. Tons of ads for bartenders, even one for a salesperson at an auto body shop!

If it is (supposedly) illegal to discriminate based on age, sex, creed, colour, national origin, etc… is it legal to discriminate based on physical attractiveness before you even meet the person?