§ 80.00 Bond resolution, or note resolution or certificate, may
contain estoppel clause. The resolution of a finance board authorizing
the issuance of bonds or notes, or the certificate of a chief fiscal
officer authorizing the issuance of notes, may, in the discretion of the
finance board or such chief fiscal officer, as the case may be, contain
a statement that the validity of such bonds or notes or any bond
anticipation notes issued in anticipation of the sale of such bonds may
be contested only if:

1. Such obligations are authorized for an object or purpose for which
the municipality, school district or district corporation is not
authorized to expend money, or

2. The provisions of law which should be complied with at the date of
the publication of such resolution or summary thereof, or certificate,
as the case may be, are not substantially complied with, and an action,
suit or proceeding contesting such validity, is commenced within twenty
days after the date of such publication, or

3. Such obligations are authorized in violation of the provisions of
the constitution.