That was because an MP cannot simply resign. A parliamentary seat is deemed to be a position of trust which can only be vacated by death, expulsion, or disqualification.
Over at the BBC Newsnight blog, Michael Crick suggested that this must have meant that Adams had made British Parliamentary history. Or that the Speaker had set a most unusual, and significant, precedent by accepting his resignation.
And Michael Crick has now added an update to his post
I’ve just asked a senior Parliamentary official whether Gerry Adams is still an MP.
“At the last count, yes he is,” he told me.
It’s all governed by the Parliamentary bible Erskine May, it seems, and the following section:
“It is a settled principle of parliamentary law that a Member, after he is duly chosen, cannot relinquish his seat; and, in order to evade this restriction, a Member who wishes to retire accepts office under the Crown, which legally vacates his seat and obliges the House to order a new writ.”
So in British law, Gerry Adams is still an MP [the MP for west Belfast], whether he wants to be or not.
Adds So the self-declared “opera-buff subversive” does have a “parachute” after all…
A full-time MP in Belfast West is, [Adams] says, essential. “The six most deprived wards in this part of the island are in this constituency, so you need to be pushing and pressing on equality and social issues.” He got more than 70% of the vote here at last year’s election, and is confident Sinn Finn can retain it at a byelection. He is less certain of winning Louth, but didn’t want to retain Belfast West as a fallback. “It isn’t a comfortable thing to leave arguably the safest seat in the galaxy, but I wanted to do that as an earnest of my intention to the people in the constituency of Louth and East Meath. I wanted to say to them, ‘I’m here and I have no parachute.'”
Further Update From Michael Crick’s blog
Update at 1915:
The Speaker’s office have been in touch: Gerry Adams remains a Member of Parliament unless or until he applies to the Chancellor for an office of profit under the Crown.