No issue or place is off-limits when a politician gets the scent of power in his or her nostrils. And so it is with US presidential hopeful Joe Biden, who gratefully seized on the UK's growing embarrassment over its proposal to break the deal Boris Johnson signed with the EU just last year.
The Internal Market Bill, if passed as it stands, would violate international law.
Mr Biden said that the Good Friday Agreement could not be allowed to become a casualty of Brexit.
He is essentially repeating the views of his fellow Democrat Nancy Pelosi, Speaker of the House of Representatives, who said no trade deal could be made between the US and UK if the new legislation was enacted.
Hers is no empty threat, because an international trade deal requires a two-thirds majority in the House of Representatives, which the Democrats currently control.
While the anti-Brexit parties in Northern Ireland welcomed Mr Biden's intervention, unionists rounded on him. That is hardly surprising.
The US was a strong supporter of the peace process, with former president Bill Clinton central to getting the Good Friday Agreement over the line.
Senator George Mitchell is also fondly remembered as an honest broker during his time in the province.
Unlike Mr Biden, whose interest in Ireland is remarkable only for his previous lack of comment, US politicians, particularly Democrats, have a long-standing interest in, and influence on, events here.
That is due in no small measure to the lobbying of the late SDLP leader John Hume, who had the vision and intelligence to realise that the dynamic of Northern Irish politics had to be changed if the sectarian conflict was to be ended.
Unionists have long been wary of US interference in Northern Ireland affairs, which is surprising given that some 23 US presidents claimed a Scots-Irish heritage.
This was a potential lode of goodwill that was never mined by unionists, who relied on the UK government to be their guarantors.
However, in this instance, the unionist parties have a valid argument when they say that the Good Friday Agreement is not the property of one section of the community and that consensus lies at its heart.
Brexit has been a very contentious issue in Northern Ireland and outside politicians should tread carefully when commenting on it.
If he gets the keys to the White House, Mr Biden could then perhaps make a more positive contribution to life here.