LONDON (Reuters) - The Scottish government on Friday published legal arguments it will use to try to persuade Britain's highest court that the devolved Scottish parliament must give its approval before Prime Minister Theresa May can trigger the Brexit process.

A High Court ruled earlier this month that the government must seek the approval of the British parliament before starting the legal process of leaving the European Union. The British government is appealing that judgment in the Supreme Court.

The nationalist Scottish government is joining the legal case, due to be heard in early December, and on Friday set out its argument in full.

It raises the threat of a delay to Brexit and an even greater constitutional puzzle - if it wins its case and if, as expected, the Scottish parliament subsequently votes against May's plan to start EU divorce proceedings by the end of March.

A majority of Scots voted to stay in the EU, in contrast to England and Wales where most voted to leave. The overall result of the June referendum was 52-48 percent in favor of leaving.

Scotland's 58-page legal document argued that any vote in the British parliament would alter the current devolution arrangements for Scotland and would therefore require a separate vote in its own devolved parliament.

"A bill brought before the UK Parliament to withdraw the UK from the EU would engage the constitutional convention in terms of which that Parliament does not normally legislate with regard to devolved matters without the consent of the Scottish Parliament," the document said.

A vote in the Scottish parliament would probably not be binding on May's government, but ignoring it would break with precedent and could pose a serious constitutional and political problem for the British leader.

(Reporting by William James; editing by Andrew Roche)