(1)    A committee required to report under this chapter may return a contribution at any time before or after it has been deposited.

   (2)   

      (a)    Except as provided in par. (b), the subsequent return of a contribution deposited contrary to law does not constitute a defense to a violation.

      (b)    A committee that accepts a contribution contrary to law, reports that contribution, and returns that contribution within 15 days after the filing date for the reporting period in which the contribution is received does not violate the contribution or source limits under this subchapter.