Assassination if nuclear scientists in Iran

You read the New York Times this morning.  US and Israeli officials quite pleased with the assassination.  Of course, neither claimed responsibility but gave justifications.  Does that mean that it is possible to provide similar justification for the assassination of Hariri by those who saw grave dangers in his secret back dealings and conspiracies?  Or are assassinations are bad only when they target friends and tools of Israel and US?  We need to understand the rules here. Of course, we know that US favor assassination of ALL Palestinians (with the exception of those on US and or Israeli payroll).