It is often said by those who want to attack unionism that it is contradictory to oppose the Brexit backstop and to support different laws on social matters.
If unionists want to be part of the United Kingdom, goes the argument, how come so many unionists oppose laws that prevail in Great Britain on matters such as language and abortion and gay marriage?
And if Northern Ireland can have differing treatment on those matters, why can it not be treated differently on EU regulations?
This is a superficially attractive argument, but a dud one. All major countries devolve certain powers to a local level. No major nation can possibly legislate for every bye-law.
But as the issue becomes of national importance, such as defence or trade, it is dealt with at a national, not a local level.
In the United States, for example, abortion and gay marriage are decided at the state level, subject to parameters which are set at the federal (ie national) level.
With regard to abortion, the 1973 Roe versus Wade ruling by the US Supreme Court set the federal parameters. It meant that every part of the nation had to allow abortion on demand in the first third of a pregnancy.
President Trump has changed the composition of the Supreme Court and it is now entirely possible that its judges will overturn Roe v Wade, and the states will have greater power to control abortion.
Alabama is heading towards a total ban on abortion, in a bid to get the Supreme Court to revisit its landmark ruling.
Those who assume that Northern Ireland must follow an inexorable path towards liberalisation on abortion should at least recognise that this is not a matter in which the political direction of travel is necessarily only one-way.
In America, pro life supporters have lost most of the major legal and political battles of the last 50 years but have never given up hope, and seem to be heading towards some victories in the legal protection of the unborn.