The Danish and Irish governments have announced that they expect to hold refendums on their countries' participation in the new European Unified Patent Court. Why hasn't the United Kingdom done likewise?

Denmark and the Republic of Ireland are burdened by written statutory constitutions, and these documents happen to require special permission before their parliaments can validly hand over power to a foreign body. In the Danish case, this is because the constitution says that outright, whereas Ireland has an American-style ban on delegating legislative or judicial authority, and since the Crotty judgment in the 1980s this has been recognised as requiring that the constitution be amended to achieve any delegations of power.

The Danish system requires a parliamentary supermajority of 5/6ths or a referendum. Amending the Irish consitution requires a referendum. So both countries are having one.

The UK, on the other hand, has a written, non-statutory constitution (it's spread across hundreds of documents). The UK's law, under the European Union Act 2011, requires a referendum when powers are transferred to the European Union, in various senses of "transferred". Effectively, this is when the EU Treaties are formally amended conferring new powers on the EU. There are lots of tricky ways of doing this, and ways of the achieving the same result, particularly by removing vetoes or changing voting requirements, and the 2011 Act goes to absurd lengths trying to categorise all of these. The Act is basically a list of all the ways the EU's treaties can be amended by the back door. Well, almost all.

Unfortunately, the EU's own constitution (its treaties) combines the worst features of French and British constitutional practice: the countries share a tradition of not really allowing the courts to "strike down" legislation, and Britain has a constitution which overtly is not contained in a single document (most countries' constitutions are not really contained in a single document. The UK has never adopted this pretence), and can evolve as a result of covert political activism by politicians, civil servants and the courts. A lot of the powers enjoyed by the EU have really been arrogated to it by European court in Luxembourg. A bunch of lobbyists decide to get a directive passed which slightly oversteps the limits of the EU's powers; so long as it has been passed by the correct legislative procedures (and the Luxembourg court is very fair on this), the Court will allow it to stand, just as the British courts let an act of Parliament stand, even if it breaches human rights.

People think the EU has an American style supreme court which strikes down legislation, but this is nonsense.

Accordingly, powers can be acquired by the EU other than by treaty amendment. The 2011 Act does not protect against this with a referendum lock. In the case of the common European patent system, the measures are being adopted slightly outside the EU's machinery anyway, and the 2011 Act only really covers formal EU matters arising from particular Treaty articles.

The Irish and Danish rules are defined in terms of who is losing power, not how it is being lost, and so cannot be circumvented by the courts or enhanced co-operation.

This is not to say that there shouldn't be a referendum in the UK about this, just that the legal argument that there has to be is by no means an open-and-shut case, and given that even discussing it involves discussing the fact that the 2011 Act is a sham means it's not likely to get discussed much.

Substantively, the patent policy is a bad one. Patents do not and should not have their own court system. The experience of the United States has been that the creation of a parellel court system for patent cases has unbalanced the patent system in favour of particular economic interest groups. Removing patent litigation from the general business of the Luxembourg court (however dishonestly that court might be interpreting the treaties) is the policy of rent-seekers.