As far as I can tell, in the United States you cannot lose your copyright, even if you don't defend it at all.
A cursory glance suggests that BYU asserts the opposite (see Myth #11) https://copyright.byu.edu/copyright-myths.
A cursory glance suggests that BYU asserts the opposite (see Myth #11) https://copyright.byu.edu/copyright-myths.
The page you've linked says: "Copyright protection is effectively never lost, unless explicitly given away or the copyright has expired. However, if you do not actively defend your copyright, there may be broader unauthorized uses than you would like."
How on earth did you read that and come to the conclusion that BYU 'asserts (sic) the opposite' ?
I’m not saying those defences would actually work. Indeed, my non-lawyer gut-feel is they probably wouldn’t. But now I’m wondering if anyone has ever tried those arguments? And if nobody has ever tried them, I think there remains a chance they might succeed, even if that chance is small. And if they ever did succeed, that would effectively amount to “defend it or lose it”, although the owner technically would not have lost the copyright, just (some of) their ability to sue infringers.