A lot of explanations and comments have been thrown around about why has the "coalition of quartets" boycotted parliament and elections, and why they advocate a change to the current constitution (or some sort of return to the constitution of 1973). Some (including a comment on this website) have suggested because they want to return to the state emergency law conditions of the 1990s! That, I find hard to believe, since it basically implies that they are masochists, who somehow get pleasure out of being detained, beaten, tortured, and deported! Anyway, I took the liberty of reading a few of their articles and talking to some of their big players just to see what their reasons are (no names, sorry, I don't want to get sued!). I've also thrown in here and there what I see as the main arguments for and against boycotting.
The first argument I've heard is that it is a matter of principle, since the National Action Charter was violated. The authorities promised one thing in the National Action Charter, and delivered another. This, the boycotters argue, is not what the government outlined, and anything that is added that was not outlined in the National Action Charter is thus strictly null and void. The opposition saw the national action charter as outlining two things: changing bahrain into a constitutional monarchy, and establishing a bicameral national assembly, where the elected branch deals solely with the legislation, and where the appointed council, in the now infamous words of the government, strictly for consultation and advice. Thus, anything else, such as making the shura have legislative powers is void of any legality.
The second argument put forward is that the elected legislative council has been so depleted, that it is basically just a scam. This does not only have to do with the appointed council having equal powers, as that is only one small part of the problem. Basically, the problem falls into two broad categories: one of legislative, and one of supervision. Let's investigate the first: the first obvious problem is that appointed council has as much authority as the legislative council. A second problem, however, is that the govt. has the right of dictating what the parliament should talk about, as the government has priority over what is discussed. Thus, over the last two years, parliament has been flooded with secondary and unimportant issues to debate about. Thirdly, the government has the right to postpone any bill passed for law in parliament for at least one whole (annual) session of parliament.Thus, any law, now matter how urgent parliament regards it, the govt. can shelf it for a while if it is not in its favour. Fourth is that the new constituion explicitly forbids changing the nature of the bicameral system. In other words, although the relative composition can change, there must be an appointed shura councial. Finally, and this is the main argument, in order to change something in the constitution, more than two thirds of the combined (both appointed and elected) house have to agree to a change in teh constitution. Even if some of the shura members vote independently of the government, there will be a large bloc who will not, and thus if the government did not the constitution to change it never will.
Basically, as a certain individual put it to me, the structure of democracy right now in Bahrain is similar to what it was in Northern Ireland not too long ago. Although notionally there is a democracy, the democracy is constructed in such a way so that ruling party (in N. Ireland this was the protestants) would win. Although MPs can debate whatever they want in Bahrain, at the end of the day, anything of material importance (such as changing the constitution) will not change unless the government wants it to. This is why the boycotters have decided to go straight to the king, since they know he is the only person who has the power to change or not to change something.
The monitoring aspect of parliament: this is another area where the boycotters feel parliament has been severely weakened comopared to 1973. The branch that deals with the supervision of government finance (deywan alraqaba al maliya i'm not sure what the exact name in english) has been taken away from parliament and placed under the king's deywan. This, the boycotters argue, makes it impossible for it to do its job of supervising government finances objectively, and also makes it very difficult for MPs to gather information regarding government spending. They point to the latest GOSI and social securities debate, where the MPs had to do the whole investigation from scratch, taking the maximum amount of time available (eight months) to conduct the investigation. If the finance supervision division was under parliament, their supervision job (which is a key job of any parliament) would be conducted much better.
This is a really good article which outlines in much more detail the above arguments: