Most jurisdictions on Earth are pretty clear that no license means no ability to use whatsoever (sans special cases like fair use), so you don't have to type "a

Most jurisdictions on Earth are pretty clear that no license means no ability to use whatsoever (sans special cases like fair use), so you don't have to type "all rights reserved" - it's the default. Sometimes the act of sharing with intention for others to use creates an implicit license though, but the extent of such license depends on particular country's laws.