UNSC establishment of tribunals is a relatively recent and somewhat unestablished power. Due to their ad hoc and hence potentially politicised nature, moves were made to create the ICC in the early 2000's. There are critics of this process on all sides of the political spectrum. To suggest that establishing 'rules' and culpability in asymmetrical warzones is possible apart from political interpretations is to divorce oneself from reality.
This does not excuse any actions, killings or the conflicts themselves. We're speaking of culpability, moral authority and the demagogic utilization of politics.
As some are pointing out, this is pure politics and theatre for Western audiences. Russia is not hostile to an investigation, but they do not accept the posturing of the resolution and the way in which it would seek to implement such an investigation.
The resolution was brought forward with full knowledge that Russia would exercise the veto. There's no genuine desire here to get to the truth of the matter. This is the United States trying to score points and to keep up public support for continued anti-Russian rhetoric as well as momentum for political machinations against the Putin regime.
It is a clear example of US mainstream media collaboration with the Establishment.
We don't know what happened to the flight. The Russians may indeed have shot it down. These things happen in war zones. The United States shot down an Iranian jetliner in the 1980's while it was inserting itself into the Iraq-Iran conflict. This is not to make light of what happened but it is to suggest that governments scheme and lie and while Putin may be head of an evil government, Samantha Power and the regime she represents have no moral standing. Will America stand for its 'heinous crimes being investigated and prosecuted'?
This Reuters piece is actually fairly neutral. The bulk of the available coverage is anti-Russian. There are of course a few media outlets which take a pro-Russian or at the very least a cynical view of the UNSC action. Their voices are not heard in the US except by those who go looking for them.