EU citizenship drive stakes more on law than politics
Today is one of those rare parliamentary occasions when Plaid Cymru gets to set the House of Commons agenda.
The party has chosen to use its time to debate European Union citizenship, as part of its campaign to allow UK nationals to retain EU citizenship after Brexit.
This would allow British citizens to work, study and live in the rest of the EU without, according to Arfon MP Hywel Williams, giving reciprocal rights to the people of the remaining 27 countries.
Plaid leader Leanne Wood told a Westminster news conference: "Central to people's identity, who they are, is the question of citizenship and to take away somebody's citizen against their will is not only wrong but it's potentially against international law as well."
In its motion for debate, Plaid have chosen to link EU citizenship with membership of the single market, which may restrict its appeal among MPs of the two main Westminster parties.
I asked Leanne Wood if she was still in denial about the 2016 referendum result. She replied: "Back in 1979 - before my time - we lost a referendum on devolution. Did Plaid Cymru at that time say, ok we accept that we're never going to have devolution in Wales? No.
"We campaigned for a further 20-odd years and we delivered devolution later on. So these things are not done and dusted with one vote. Political issues carry on and this is something that's going to be live for quite some time."
Back in 1975, Hywel Williams was one of the Plaid members who voted for Britain to remain in the EEC (most of the party voted to leave). Ahead of the debate, he said: 'I am European - a Welsh European - and no government, no state and no Brexiteer should be allowed to take that away from me or anyone else."
But the UK government said: "The EU treaty provisions state that only citizens of EU member states are able to hold EU citizenship. Therefore, when the UK ceases to be a member of the European Union, British nationals will no longer hold EU citizenship unless they hold dual nationality with another EU member state.
"However, we know that in the future, many UK nationals will wish to continue to travel, live and work within the European Union, just as EU citizens will still wish to do so in the UK. We look forward to discussing our future relationship with the European Union, one which will work in the interest of both the UK and the EU."
Plaid's hopes are based more on the legal case - as advanced by Prof Volker Roeben - than on the politics. One senior Labour MP complained that Plaid Cymru had not tried to engage with his party. "It's not reaching anyone beyond the Plaid Cymru vote," he said. "This is student politics."
It's possible the campaign is targeted at Plaid's core vote - although it's supported by the Liberal Democrats and Greens too. The news conference used a backdrop featuring both Plaid's own logo and the EU stars - from a flag the anti-Brexit group "Cardiff for Europe" recently suggested is a bit of a "turn-off" to "soft, undecided voters".
My colleague David Williamson from Wales Online asked the politicians how likely - on a scale of one to 10 - the campaign was likely to succeed.
None of the replies included a number.
UPDATE: The Plaid Cymru motion was passed without a vote - the first time a Plaid motion has been approved by the Commons - but the result isn't binding on the government. Conservative MPs are often told to abstain during opposition-led debates - last year, for example, MPs voted unanimously to pause the roll-out of Universal Credit but the policy does not appear to have changed.