Common-sense rights: The coalition's record on civil liberties has been disappointing

Plenty of countries can take away your passport at the stroke of a pen, but they tend to be places like North Korea

The decline of this government's commitment to civil liberties has been disappointing. The Conservative Party went through a curious phase in opposition, rediscovering its love of the British tradition of liberty and the rule of law. Mostly, this was led by David Davis, the then Shadow Home Secretary, who quixotically resigned his seat in 2008 to fight a by-election in protest against New Labour's authoritarianism. But enough of his liberal Conservatism survived to make it easier for the party under David Cameron to make common cause with the Liberal Democrats after the last election. Since then, the coalition's record has been unimpressive.

True, one of its early acts was to cut the maximum period for which terrorist suspects could be held before being charged, which Labour had tried and failed to increase, first to 90 days and then to 42 days. It was Theresa May, Mr Cameron's unexpected choice as Home Secretary, who halved it from 28 days to 14 days. That was a welcome step in the right direction, but since then the attachment of both coalition parties to the principles of liberty seems to have been weakening.

Ms May has been increasingly assertive in her opposition to the European Court of Human Rights, and even to the Convention, which is incorporated into British law in the Human Rights Act. Mr Cameron's sacking of Dominic Grieve last July was ominous. As Attorney General, Mr Grieve was the Government's principal legal adviser and a senior minister with the right to attend Cabinet, but he was also a staunch defender of human rights law even when – especially when – it annoyed ministers. Nick Clegg has held the line on this for the time being, but, generally, as Philippe Sands said last month, he has been "very disappointing". Mr Sands was talking about Mr Clegg's reaction to allegations of British involvement in torture: "He's had ample opportunity to uncover, as Deputy Prime Minister, what was going on. We've now pushed it off to a rather pitiful parliamentary committee with no teeth... and again it just goes into the long grass."

This week brings an important test for both coalition parties. The Counter-Terrorism and Security Bill returns to the Commons for its report stage. One of its provisions would give the Home Secretary the power to take away the passports of alleged jihadis attempting to return to the UK from Syria or Iraq. This is a draconian and arbitrary power, at odds with the British principles of due process. It is not a power that should be in the hands of a politician without safeguards.

As Mr Davis tells The Independent on Sunday: "There are plenty of countries that can take away your passport at the stroke of a pen, but they tend to be places like North Korea."

In any event, the measure would be likely to be counterproductive. It makes more sense to treat British people returning from areas controlled by the so-called Islamic State warily but decently. They may have valuable intelligence – we wonder what the security services make of Ms May's proposals – and may be returning disillusioned, in which case they might help to dissuade others from following their example.

Yvette Cooper, the Shadow Home Secretary, has tabled an amendment that would require the Home Secretary's decision to be approved by a court. As we report today, several Conservatives, including Mr Davis, and some more Liberal Democrats are likely to support Labour's amendment. This may seem a fairly minor question, but it is an important test of civil liberties principle. Mr Cameron and Ms May should do the right thing and concede the point before they are needlessly and counterproductively embarrassed in the voting lobbies in the House of Commons.