Most of the European companies adopted the new scheme within their current contracts, so it was a technical thing. Russia just needed to be paid in currency that can not be stolen by some lunatic government.
Even freezing of central bank accounts is basically the unilateral unlawful change of contract.
Finland broke the contract with russian railroads, with russian electric providers, it cancelled the contract with RosAtom.
Additionally it started the process of joining NATO, which effectively breaks the peace treaty of 1948.