The country has the right to govern itself without interference from other countries. This includes in any affairs including Currency. The state has the right to make currency as a medium of exchange to crush the country's economy. But you need to know that every country sometimes has dependence on foreign countries so there are decisions that might make them not go well, including legalizing bitcoin as a currency.

Since the IMF has announced against the use of bitcoin, they even gave El Salvador a threat. The IMF or World Bank will not provide financial assistance to El Salvador. So many countries certainly think repeatedly because of this fear. So all countries can accept Bitcoin payments but there are risks that they have to get.  No one is able to intervene in the government of a country. CMIIW

Source: https://ww1.odu.edu/content/dam/odu/offices/mun/docs/4th-non-interference.pdf