If one is mistaken about whether consent is required, is that a defence to sexual assault in Canada or similar jurisdictions?

Question

In "Canadian man found not guilty of raping wife", a sexual assault prosecution failed due to mens rea because it wasn't proved that the man knew his behaviour was illegal. Not because he didn't know that the sex was not consensual, just that he thought non-consensual sex was legal (it has been in a wide variety of jurisdictions belonging to many different cultures, and still is in others).

Has such a defense been used before, either in Canada, or other countries with a similar legal system, such as the UK or Australia, for sex without consent? If so, have courts decided whether or not it is a valid defense, and if it has been ruled a valid defense, have such cases been appealed?

The section on mens rea in the Wikipedia article "Laws regarding rape" only talks about ignorance about whether the sex was consensual. The section Ignorance of the law and mens rea gives as an example someone making a mistake with their taxes, which seems fairly different to the scenario discussed here.

Answer 1

This judgment (R. v. H.E., 2017 ONSC 4277) was overturned on appeal (2018 ONCA 879):

[2] After accepting the complainant’s testimony that both she and Mr. E. believed that, as his wife, she did not have the right to refuse to have sex with him, the trial judge explained the acquittal by expressing a reasonable doubt about whether Mr. E. had the required mens rea for the offence. ...

[3] Mr. E. concedes that the trial judge committed reversible errors in this reasoning. He acknowledges that to the extent the trial judge based his acquittal on Mr. E.’s and the complainant’s shared belief that the complainant could not refuse to have sex with him, that belief would be a mistake of law that cannot form the foundation for an honest but mistaken belief in consent defence. He is correct. To avoid conviction based on an honest but mistaken belief in consent, the accused must believe in a state of facts that amount to consent according to law...

...

[6] The parties therefore agree that the appeal must be allowed and the verdict of acquittal set aside....

[7] We would therefore allow the appeal, set aside the acquittal, and order a new trial.