You could get around it by advertising a senior position, for which women applicants are sought, and a junior position, where everyone will be considered, with substantially the same responsibilities but different pay.

Would a US court disallow this? It doesn't seem to violate the spirit of affirmative action, or the letter of equality laws.

That's true, I didn't think of that. It does seem like it would be a more direct way for them to increase the number of women that work there though. To me it doesn't feel worse than allowing a numeric quota.

I suppose individual women are free to negotiate a higher salary.