Disable currency selector based on country

Dear Support Team!

I have a little bit of a legal problem. How can I force customers in certain countries to only use one currency?

The issue: inside the EU, if the invoice has been made in any currency other than euros, the tax amount must also be stated in euros and the exchange rate from that day must be printed on the invoice

My proposed solution: in order to not have to deal with all these issues, it would be great to just disable paying in any other currency than the Euro if the billing country is a EU country.

I have two ideas how that is achievable, but I don’t know how to implement either of them. If you feel that there is a simpler way, please share it with me!

1. Somehow remove the currency selector (or lock it to EUR) when the country at checkout is set to an EU country (I have already set all EU countries in the WMC Plugin> Location > Countries with default currency EUR or
2. Create a condition where the payment button on the checkout fails (with a message) if currency is not set to EUR and billing_country is an EU country

Is any of this possible? Is there a simpler way?

Thank you in advance for your hard work!

Best,
Christian