Which international law?
Serious question. I want to look it up.
Legality of Israeli settlements - Wikipedia

Chapter 3: Israeli Settlements and International Law

Interview with Dr. Mark Ellis : Israeli Settlements under International Law
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Israel’s Settlements Have No Legal Validity, Constitute Flagrant Violation of International Law, Security Council Reaffirms | Meetings Coverage and Press Releases
14 Delegations in Favour of Resolution 2334 (2016) as United States Abstains The Security Council reaffirmed this afternoon that Israel’s establishment of settlements in Palestinian territory occupied since 1967, including East Jerusalem, had no legal validity, constituting a flagrant violation...
Now the US doesn't recognize these things as "Illegal", but it suits them to ignore the actual reality/facts of it.
But just because the US "doesn't recognize it", doesn't mean it's not illegal, especially not when the Security Council (without the US, who abstained, of course) affirmed that yes, they are illegal.
As an aside, Canada's stance:
Occupied Territories and Settlements
Canada does not recognize permanent Israeli control over territories occupied in 1967 (the Golan Heights, the West Bank, East Jerusalem and the Gaza Strip). The Fourth Geneva Convention applies in the occupied territories and establishes Israel's obligations as an occupying power, in particular with respect to the humane treatment of the inhabitants of the occupied territories. As referred to in UN Security Council Resolutions 446 and 465, Israeli settlements in the occupied territories are a violation of the Fourth Geneva Convention. The settlements also constitute a serious obstacle to achieving a comprehensive, just and lasting peace.
Canada believes that both Israel and the Palestinian Authority must fully respect international human rights and humanitarian law which is key to ensuring the protection of civilians, and can contribute to the creation of a climate conducive to achieving a just, lasting and comprehensive peace settlement.