Yes (at least, in the UK). The brief here:

http://www.parliament.uk/business/publications/research/brie...

Mentions the "The Human Fertilisation and Embryology Act 2008" which banned implantation of a genetically modified embryo. There is a provision in that act for Parliament to approve regulations that provides exceptions for the treatment of mitochondrial diseases.

More: Here's the section of the act:

http://www.legislation.gov.uk/ukpga/2008/22/section/26

Yes, it was explicitly banned in 1990, with the Human Fertilisation and Embryology Act. In 2008 the government modified the act to allow mitochondrial transfer under future regulations, which enabled such research to take place on human tissue [1].

[1] Section 4 of http://www.legislation.gov.uk/ukdsi/2015/9780111125816/pdfs/...

(I wasn't) correct in saying that the implantation of modified embryos was banned in 2008:

http://www.legislation.gov.uk/ukpga/2008/22/section/3

Here's the relevant original text:

http://www.legislation.gov.uk/ukpga/1990/37/section/3/enacte...

edited for error.

Perhaps I'm reading this incorrectly, but as far I can see it was implicitly banned in the 1990 Act by section 3(3d). And then section 3ZA(5) as introduced in 2008 enabled the development of oocyte or embryo-modifying technologies to prevent mitochondrial disease.

I think you're right, sorry for the noise.

No I think we're both correct - sorry, I didn't explain myself properly! I agree with you that it was definitely still banned for implantation.

But by having that clause about mitochondrial disease in, it enabled researchers to investigate (and the the HFE Authority to permit research on) human mitochondrial transfer techniques in vitro by explicitly pointing out the possibility of a future redefinition.

EDIT: this explains it much better than I'm trying to - http://www.hfea.gov.uk/mitochondrial-disease-new-research.ht...