the Nigerian government has no control over what forex brokers do, if you opan an account with any forex broker you are dealing with a foreign company so if something goes wrong it is not the Nigerian governments business.
However Nigerians have been trading forex with these foreign brokers for years and only a few bad incidents have occured to my knowledge. So, its your risk to take.
Another emerging threat is prop firms and those ones are not regulated in any country at all but people still trade with them.