Uh, in the case of search and seizure, it explicitly is. The Fourth Amendment provides a standard for searching the property of criminals. Such searches are carried out routinely with no issues. There are other standards for "violating" other rights to privacy also.

I'm not saying criminals don't deserve rights. In fact, what's at stake here is that the Fifth Amendment does protect a mass murderer from revealing his passcode, so I'm not sure what you and all these downvoters are going on about. If criminals didn't have rights there wouldn't be an issue here.

If the passcode on the phone were crackable, it would be absolutely 100% legal to search it. And that kind of thing happens routinely. The issue at stake is not searching the phone, but compelling Apple to help with the search.