Currently all Opus One guitars have ribs (sides) and backs of Indian rosewood. Brazilian rosewood is by general consent the best wood for the job, but it is virtually unobtainable, while Indian rosewood is almost as good and so far not too difficult to obtain. (This applies to traditionally fan-braced guitars—lattice-bracing is a different story.)
However, Dalbergia, to which species rosewood belongs, has now become endangered as a result of hugely increased demand, and CITES (the Convention on International Trade in Endangered Species) has made it illegal to trade in any kind of rosewood across national borders.
Fortunately Opus One’s supplier has an adequate stock of rosewood at present and—like Opus One—is based in the UK, so for the time being there is no problem, for EU purchasers at least. The situation may well change however, and if so it may become impossible to continue to use rosewood. What to use instead should this happen is an open question.
The CITES regulations (which, incidentally, have the force of law) are quite strict. They stipulate that rosewood, including articles made of rosewood, may only be taken across national borders in quantities weighing not more than 10 kilograms, and provided they are not being transferred for commercial purposes. So if you have bought an Opus One guitar in the UK and wish to take it abroad you should be OK, provided you have already paid for it (keep the receipt handy!), and the customs officials at both ends are aware of and understand the regulations.
Personally I wouldn’t risk it; people have been known to have their guitars confiscated!
This also means, of course, that it would be against the CITES regulations for Opus One to sell guitars (containing rosewood) to people who are residing outside the EU (or, if and when Brexit actually happens, the UK).
For a more in-depth consideration of this question see www.wood-database.com/wood-articles/rosewoods-bubinga-really-banned-cites/.