Yes, policy should be written in the Ops Manual. Also, fuel requirements are based on what is required by your operating certificate, not what some other regulator around the world might think. OTOH, most regulators frown upon landing with 0 usable fuel remaining...
Our Dispatch Release includes a Minimum Fuel for Takeoff, which includes all required reserves. Once airborne, headwinds or other delays may eat into reserves.
I use my personal minimum landing fuel plus fuel to alternate as the minimum acceptable landing fuel at destination. If something happens that puts projected landing fuel below that figure, I start looking for alternatives.
Thankfully, not every possible contingency is written into regulations. That's why they pay Captains extra money to think and decide...