Obtaining U.S. Citizenship After Parent Denounced Their U.S. Citizenship

[homeward.bound]

I am American. My husband is Australian. We currently reside in Australia.

We are looking at moving to the states and are not sure which avenue to pursue, for him to obtain his US Citizenship.

While we could try to go the spousal route, his father was a US citizen, born and raised. He denounced his citizenship after moving to Australia. We are unsure of the time frame of when this was done - ie, if it was before or after my husband's birth - but it was sometime in the early 70s we assume.

Would he have any claim on citizenship via the father?

Any help you guys/gals could offer would be greatly appreciated.

[Mr. Knowitall]

How old was he at the time of denunciation? Was this a formal denunciation made to the U.S. government, or was this a statement he made during the oath of citizenship for Australia?