Separation of Powers question

I don't understand why this would be a violation of the separation of powers. Each branch has powers, this is one given to the vice president.

The president can veto legalisation, do you consider that a violation of separation of powers? The Congress can block cabinet nominees, is that a violation?

He hasn't vetoed the legalisation of marijuana in Colorado, I think. Is he a stoner?

It's a check on the senate, albeit a very lame, not so particularly power check as you might be implying.

All things considered, it's a rare practice given how many hundreds of bills go through the senate in a give year.

List of tie-breaking votes cast by vice presidents of the United States