Senior ministers concerned about effects of Occupied Territories Bill.

Ireland left the UK and acheived international recognition as an independent sovereign state. Tibet never did. Therefore, when the Chinese reasserted control in Tibet in 1952, they were acting within internationally-recognised Chinese territory.

International law no longer accepts imperialist conquest as a legitimate method of establishing a state, or extending the territory of a state. But that is a second-half-of-the-twentieth-century development. We live in a world in which many — perhaps most — of the states that exist now were established, or had their borders determined, by these means. International law doesn't retrospectively nullify the existence or territorial extent of those states (and, for obvious reasons, supporters of Israel wouldn't wish it to). But a consequence of that is that Chinese actions in Tibet, deplorable as they may be, are not regarded as an illegal occupation. Similarly, Chinese actions in Uighir territories may be deplorable, and may violate international law in various ways, but they are not in unlawful occupation of territory which is not their own.

Tl;dr: You can't shoehorn Tibet into the Israel-in-Palestine model; it's a materially different problem.

Palestine was run by the British as a League of Nations mandate - a colony in all but name. In 1947, the UN published a partition plan that would've been a two-state solution, under which a UN administration would've ruled Jerusalem. The Jews accepted the plan but most Arabs did not. In 1948, the British Mandate ended. Therefore, given that Ghana had the same borders as the Gold Coast, why was Israel in 1948 not allowed to have the same borders as Palestine?

Because then it wouldn't have been Israel — it would have been Palestine, an Arab state with a large Jewish minority (30-35%) in it. That wasn't, obviously, what the Zionist movement was seeking — hence, partition. This explains why Jews mostly accepted partition but Arabs mostly did not.

(While most postcolonial states acheived independence with unchanged borders, Palestine isn't the only example of partition on independence. There's also India, Korea, Vietnam and, of course, Ireland. From this list we can see that partitioning on independence tends, on the whole, not to work out well.)

In 1948, Israel didn't invade - Jordan and Egypt and other Arab nations did. In 1967, those nations attacked Israel again. So why is it that, from 1948 to 1967, Jordan was not labelled as an occupier of the West Bank & East Jerusalem but, today, Israel is? Surely, international law today can't be much different from the first five years after World War Two.

(Nitpick: Arab nations didn't attack Israel in 1967; the 6-day war started with an Israeli surprise attack on Egypt.)

Jordan was indeed an occupying power in the West Bank from 1948 to 1967, and was so regarded by the international community, including by other Arab states. The occupation was formalised by the 1949 armistice agreement that marked the end of hostilities in the 1948 Arab-Israeli war. (The armistice agreement also provided for Egypt to occupy and administer the Gaza strip, and that occupation also continued until 1967.)

The occupation of the West Bank was not fundamentally different the occupations of parts or all of France, Italy, Germany, Austria, Japan, etc that went on during and after the Second World War, some of which were still ongoing in 1948. Occupation in the course of, or in the aftermath of, a war is accepted and regulated by international law — specifically, the Fourth Geneva Convention. It's not automatically illegal.

In 1950 Jordan annexed the West Bank — declared it to be part of Jordan. That was illegal, and almost no states recognised or accepted it. The Arab League condemned it. Jordan lost the West Bank in the 1967 War, but it didn't renounce its formal claim to the territory until 1988.

Israel has been in occupation of the West Bank since 1967. The occupation wasn't initially illegal, any more than Jordan's had been. It became illegal when it ceased to be temporary, and when Israel started governing the West Bank in violation of the Fourth Geneva Convention — establishing settlements; colonising the area by importing and its own population; annexing territory (East Jerusalem);

It's absurd to say that the US would never sanction the EU, given that the US has already sanctioned the EU on more than one occasion.

Plus I think you concede the point yourself, when you say that sanctions on Ireland could be imposed as a pre-emptive warning to the EU not to follow suit. How could the US given a credible and effective warning about something that it would never do?

So, there's a non-zero chance that collective action by the EU would attract a US response.

But it's not a slam-dunk that the existence of a non-zero chance of an unspecified US response means that Ireland, or the EU, should take no action. You have to join the dots needed to complete that argument before anybody is going to find it persuasive. You need to qualify the chance as best you can. You also — and this is a bigger gap in the argument as it stands — need to look at what action the US would actually take, and how that would affect Ireland/the EU. The US actually has anti-boycott legislation, providing for the measures it will take in response to boycotts that the US doesn't support. What does that legislation say? How would those measures, if taken, affect Ireland? Or do you want to argue that they would ignore that legislation, and do something else entirely?