It's fast becoming one of the biggest constitutional issues in recent years.
The bill is currently being debated in the Lords
After a marathon all-night session in Westminster, the debate on the Prevention of Terrorism Bill is ping-ponging to and from the Commons and the Lords.
It coincides with Liberal Democrat leader Charles Kennedy cancelling a visit to his party's Welsh conference in Cardiff as the debate threatens to spill over the weekend.
The BBC Wales news website caught up with four MPs to get a temperature reading from the main political parties:
Huw Irranca-Davies, Labour MP for Ogmore
"There doesn't seem to be any give at all from the opposition benches.
Labour MP Huw Irranca-Davies said the opposition was not moving
"John Denham, the former police minister, made a powerful speech in which he said 'We have had differences in points of principle before, but ultimately, wherever there has been this stand-off between the Lords and the Commons, always, in past occurrences, the Lords eventually said we recognise the will of the Commons'.
"What we are not seeing unfortunately is any will at all to move from the other side, and that will mean we will have people who are under suspicion from the security services walking the streets this weekend."
He added that improvement to the bill was needed, but said these could be made over the coming months, rather than imposing a time limit, or "sunset clause" on the legislation.
Nigel Evans, Conservative MP for Ribble Valley and former shadow Welsh secretary
"I am somewhat tired but quite frankly, what we are debating is so fundamentally important to the human rights of people in this country, that I think it is right that we have decided to go right through the night.
Nigel Evans accused Tony Blair of acting arrogantly
"At this moment in time, I can tell you, we don't know when it is going to end.
"What we are looking for is major concessions from the government on this piece of legislation that has now been sent back several times by peers of all political persuasion.
"The sense we are getting from the House of Lords is they are not prepared to cave in.
He said the only way the situation would be resolved was for Tony Blair and Home Secretary Charles Clarke to stop acting in an "arrogant way".
Elfyn Llywd, Plaid Cymru MP for Meirionnydd Nant Conwy
"I don't see there's any compromise in the air, but I agree there are fundamental things need putting right.
Elfyn Llwyd described the bill as "frightening"
"It's a frightening bill - we should have had much more time, we should have been discussing this over the last month.
"This has been rushed through in the most appalling way.
"Somebody can suspect you or I and we can be held under house arrest - we will not know the case against us, we will not be allowed to be properly represented."
He said the proposed bill went against "any basic principles of justice known to any legal system anywhere".
Lembit Ípik, Liberal Democrat MP for Montgomeryshire
Mr Ípik said it was the "biggest deadlock" he had known in Parliament.
Lembit Ípik said he had written off Friday
"I have never known anything like this in terms of resolve from the Lords, who are simply saying, we do not agree with where the government wants to take this terror legislation and we are going to hold out.
"My guess is that every member of parliament and every member of the house of lords is writing off Friday, and it could go as far as Saturday or Sunday.
"It feels that for once, the opposition parties have got together and are really making a stand against what we think is very dangerous legislation."